Remove `prefer_equal_for_default_values` lint rule (#120533)

* Remove `prefer_equal_for_default_values` lint rule

* Remove prefer_equal_for_default_values line

analysis_options.yaml

@@ -153,7 +153,6 @@ linter:
     # - prefer_constructors_over_static_methods # far too many false positives
     - prefer_contains
     # - prefer_double_quotes # opposite of prefer_single_quotes
-    - prefer_equal_for_default_values
     # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
     - prefer_final_fields
     - prefer_final_in_for_each