[pylint] Fix PLC2801 autofix creating a syntax error (#18857)

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## Summary
This PR fixes `PLC2801` autofix creating a syntax error due to lack of
padding if it is directly after a keyword.

Fixes https://github.com/astral-sh/ruff/issues/18813
<!-- What's the purpose of the change? What does it do, and why? -->

## Test Plan
Add regression test
<!-- How was it tested? -->

crates/ruff_linter/resources/test/fixtures/pylint/unnecessary_dunder_call.py

@@ -129,3 +129,6 @@ blah = dict[{"a": 1}.__delitem__("a")]  # OK
 
 # https://github.com/astral-sh/ruff/issues/14597
 assert "abc".__str__() == "abc"
+
+# https://github.com/astral-sh/ruff/issues/18813
+three = 1 if 1 else(3.0).__str__()

crates/ruff_linter/src/rules/pylint/rules/unnecessary_dunder_call.rs

@@ -4,6 +4,7 @@ use ruff_python_semantic::SemanticModel;
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
+use crate::fix::edits;
 use crate::rules::pylint::helpers::is_known_dunder_method;
 use crate::{Edit, Fix, FixAvailability, Violation};
 use ruff_python_ast::PythonVersion;
@@ -232,7 +233,7 @@ pub(crate) fn unnecessary_dunder_call(checker: &Checker, call: &ast::ExprCall) {
         }
 
         diagnostic.set_fix(Fix::unsafe_edit(Edit::range_replacement(
-            fixed,
+            edits::pad(fixed, call.range(), checker.locator()),
             call.range(),
         )));
     }

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLC2801_unnecessary_dunder_call.py.snap

@@ -1193,6 +1193,8 @@ unnecessary_dunder_call.py:131:8: PLC2801 [*] Unnecessary dunder call to `__str_
 130 | # https://github.com/astral-sh/ruff/issues/14597
 131 | assert "abc".__str__() == "abc"
     |        ^^^^^^^^^^^^^^^ PLC2801
+132 |
+133 | # https://github.com/astral-sh/ruff/issues/18813
     |
     = help: Use `str()` builtin
 
@@ -1202,3 +1204,21 @@ unnecessary_dunder_call.py:131:8: PLC2801 [*] Unnecessary dunder call to `__str_
 130 130 | # https://github.com/astral-sh/ruff/issues/14597
 131     |-assert "abc".__str__() == "abc"
     131 |+assert str("abc") == "abc"
+132 132 | 
+133 133 | # https://github.com/astral-sh/ruff/issues/18813
+134 134 | three = 1 if 1 else(3.0).__str__()
+
+unnecessary_dunder_call.py:134:20: PLC2801 [*] Unnecessary dunder call to `__str__`. Use `str()` builtin.
+    |
+133 | # https://github.com/astral-sh/ruff/issues/18813
+134 | three = 1 if 1 else(3.0).__str__()
+    |                    ^^^^^^^^^^^^^^^ PLC2801
+    |
+    = help: Use `str()` builtin
+
+ℹ Unsafe fix
+131 131 | assert "abc".__str__() == "abc"
+132 132 | 
+133 133 | # https://github.com/astral-sh/ruff/issues/18813
+134     |-three = 1 if 1 else(3.0).__str__()
+    134 |+three = 1 if 1 else str(3.0)