Fix formatter panic with comment after parenthesized dict value (#5293)

## Summary

This snippet used to panic because it expected to see a comma or
something similar after the `2` but met the closing parentheses that is
not part of the range and panicked
```python
a = {
    1: (2),
    # comment
    3: True,
}
```

Originally found in
636a717ef0/testing/marionette/client/marionette_driver/geckoinstance.py (L109)

This snippet is also the test plan.

crates/ruff_python_formatter/src/comments/placement.rs

@@ -991,14 +991,22 @@ fn handle_dict_unpacking_comment<'a>(
     .skip_trivia();
 
     // we start from the preceding node but we skip its token
-    if let Some(first) = tokens.next() {
-        debug_assert!(matches!(
-            first,
-            Token {
-                kind: TokenKind::LBrace | TokenKind::Comma | TokenKind::Colon,
-                ..
-            }
-        ));
+    for token in tokens.by_ref() {
+        // Skip closing parentheses that are not part of the node range
+        if token.kind == TokenKind::RParen {
+            continue;
+        }
+        debug_assert!(
+            matches!(
+                token,
+                Token {
+                    kind: TokenKind::LBrace | TokenKind::Comma | TokenKind::Colon,
+                    ..
+                }
+            ),
+            "{token:?}",
+        );
+        break;
     }
 
     // if the remaining tokens from the previous node is exactly `**`,

crates/ruff_python_formatter/src/snapshots/ruff_python_formatter__tests__ruff_test__expression__dict_py.snap

@@ -54,6 +54,14 @@ mapping = {
     C: 0.1 * (10.0 / 12),
     D: 0.1 * (10.0 / 12),
 }
+
+# Regression test for formatter panic with comment after parenthesized dict value
+# Originally found in https://github.com/bolucat/Firefox/blob/636a717ef025c16434997dc89e42351ef740ee6b/testing/marionette/client/marionette_driver/geckoinstance.py#L109
+a = {
+    1: (2),
+    # comment
+    3: True,
+}
 ```
 
 
@@ -112,6 +120,14 @@ mapping = {
     C: 0.1 * (10.0 / 12),
     D: 0.1 * (10.0 / 12),
 }
+
+# Regression test for formatter panic with comment after parenthesized dict value
+# Originally found in https://github.com/bolucat/Firefox/blob/636a717ef025c16434997dc89e42351ef740ee6b/testing/marionette/client/marionette_driver/geckoinstance.py#L109
+a = {
+    1: (2),
+    # comment
+    3: True,
+}
 ```