Add and apply Style/RedundantRegexpArgument RuboCop rule

This rule was introduced in RuboCop 1.53.0. After adding the
Style/RedundantRegexpCharacterClass rule in the previous commit,
RuboCop started detecting redundant regular expression arguments.
Therefore, we apply this rule to remove them and prevent future
occurrences.

.rubocop.yml

@@ -781,6 +781,9 @@ Style/RedundantInterpolation:
 Style/RedundantParentheses:
   Enabled: true
 
+Style/RedundantRegexpArgument:
+  Enabled: true
+
 Style/RedundantRegexpCharacterClass:
   Enabled: true