Improve B005 documentation to reflect duplicate-character behavior (#7601)

## Summary

B005 only flags `.strip()` calls for which the argument includes
duplicate characters. This is consistent with bugbear, but isn't
explained in the documentation.

crates/ruff_linter/src/rules/flake8_bugbear/rules/strip_with_multi_characters.rs

@@ -21,14 +21,25 @@ use crate::checkers::ast::Checker;
 /// `str.removesuffix` to remove an exact prefix or suffix from a string,
 /// respectively, which should be preferred when possible.
 ///
+/// ## Known problems
+/// As a heuristic, this rule only flags multi-character strings that contain
+/// duplicate characters. This allows usages like `.strip("xyz")`, which
+/// removes all occurrences of the characters `x`, `y`, and `z` from the
+/// leading and trailing ends of the string, but not `.strip("foo")`.
+///
+/// The use of unique, multi-character strings may be intentional and
+/// consistent with the intent of `.strip()`, `.lstrip()`, or `.rstrip()`,
+/// while the use of duplicate-character strings is very likely to be a
+/// mistake.
+///
 /// ## Example
 /// ```python
-/// "abcba".strip("ab")  # "c"
+/// "text.txt".strip(".txt")  # "ex"
 /// ```
 ///
 /// Use instead:
 /// ```python
-/// "abcba".removeprefix("ab").removesuffix("ba")  # "c"
+/// "text.txt".removesuffix(".txt")  # "text"
 /// ```
 ///
 /// ## References
@@ -39,7 +50,7 @@ pub struct StripWithMultiCharacters;
 impl Violation for StripWithMultiCharacters {
     #[derive_message_formats]
     fn message(&self) -> String {
-        format!("Using `.strip()` with multi-character strings is misleading the reader")
+        format!("Using `.strip()` with multi-character strings is misleading")
     }
 }
 
@@ -65,8 +76,7 @@ pub(crate) fn strip_with_multi_characters(
         return;
     };
 
-    let num_chars = value.chars().count();
-    if num_chars > 1 && num_chars != value.chars().unique().count() {
+    if value.chars().count() > 1 && !value.chars().all_unique() {
         checker
             .diagnostics
             .push(Diagnostic::new(StripWithMultiCharacters, expr.range()));

crates/ruff_linter/src/rules/flake8_bugbear/snapshots/ruff_linter__rules__flake8_bugbear__tests__B005_B005.py.snap

@@ -1,7 +1,7 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_bugbear/mod.rs
 ---
-B005.py:4:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:4:1: B005 Using `.strip()` with multi-character strings is misleading
   |
 2 | s.strip(s)  # no warning
 3 | s.strip("we")  # no warning
@@ -11,7 +11,7 @@ B005.py:4:1: B005 Using `.strip()` with multi-character strings is misleading th
 6 | s.strip("\n\t ")  # no warning
   |
 
-B005.py:7:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:7:1: B005 Using `.strip()` with multi-character strings is misleading
   |
 5 | s.strip("e")  # no warning
 6 | s.strip("\n\t ")  # no warning
@@ -21,7 +21,7 @@ B005.py:7:1: B005 Using `.strip()` with multi-character strings is misleading th
 9 | s.lstrip("we")  # no warning
   |
 
-B005.py:10:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:10:1: B005 Using `.strip()` with multi-character strings is misleading
    |
  8 | s.lstrip(s)  # no warning
  9 | s.lstrip("we")  # no warning
@@ -31,7 +31,7 @@ B005.py:10:1: B005 Using `.strip()` with multi-character strings is misleading t
 12 | s.lstrip("\n\t ")  # no warning
    |
 
-B005.py:13:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:13:1: B005 Using `.strip()` with multi-character strings is misleading
    |
 11 | s.lstrip("e")  # no warning
 12 | s.lstrip("\n\t ")  # no warning
@@ -41,7 +41,7 @@ B005.py:13:1: B005 Using `.strip()` with multi-character strings is misleading t
 15 | s.rstrip("we")  # warning
    |
 
-B005.py:16:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:16:1: B005 Using `.strip()` with multi-character strings is misleading
    |
 14 | s.rstrip(s)  # no warning
 15 | s.rstrip("we")  # warning
@@ -51,7 +51,7 @@ B005.py:16:1: B005 Using `.strip()` with multi-character strings is misleading t
 18 | s.rstrip("\n\t ")  # no warning
    |
 
-B005.py:19:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:19:1: B005 Using `.strip()` with multi-character strings is misleading
    |
 17 | s.rstrip("e")  # no warning
 18 | s.rstrip("\n\t ")  # no warning
@@ -61,7 +61,7 @@ B005.py:19:1: B005 Using `.strip()` with multi-character strings is misleading t
 21 | s.strip("あ")  # no warning
    |
 
-B005.py:22:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:22:1: B005 Using `.strip()` with multi-character strings is misleading
    |
 20 | s.strip("a")  # no warning
 21 | s.strip("あ")  # no warning
@@ -71,7 +71,7 @@ B005.py:22:1: B005 Using `.strip()` with multi-character strings is misleading t
 24 | s.strip("\u0074\u0065\u0073\u0074")  # warning
    |
 
-B005.py:24:1: B005 Using `.strip()` with multi-character strings is misleading the reader
+B005.py:24:1: B005 Using `.strip()` with multi-character strings is misleading
    |
 22 | s.strip("ああ")  # warning
 23 | s.strip("\ufeff")  # no warning