Add and apply Style/RedundantRegexpCharacterClass rubocop rule

This rule was introduced in RuboCop 0.93.0, but now after seeing a fix in version 1.65,
we have decided to add it. The reason for adding it is to simplify our regular
expressions. This enforcement will help us maintain better regular expression
practices across the project.

.rubocop.yml

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