Remove bogus comment from parseLiteralSetOrMapSuffix

This comment was relevant in a previous revision of the patterns
parsing logic and I neglected to revert it.

Bug: #50035
Change-Id: Ia4034d66c3cc354e2ea6f2e1485380bccf7333dd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/261700
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Jens Johansen <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

pkg/_fe_analyzer_shared/lib/src/parser/parser_impl.dart

@@ -6348,8 +6348,6 @@ class Parser {
 
   /// This method parses the portion of a set or map literal that starts with
   /// the left curly brace when there are no leading type arguments.
-  ///
-  /// [forPattern] indicates whether an expression or pattern should be parsed.
   Token parseLiteralSetOrMapSuffix(Token token, Token? constKeyword) {
     Token leftBrace = token = token.next!;
     assert(optional('{', leftBrace));