Remove invalid EnableNewCops config key from Pro RuboCop config

The correct RuboCop syntax is 'NewCops: enable' under AllCops, which is
already defined in the root .rubocop.yml that this config inherits from.
'EnableNewCops: true' is not a valid RuboCop configuration key and will
be silently ignored.

Co-authored-by: Ihab Adham <ihabadham@users.noreply.github.com>

Author: github-actions[bot]

react_on_rails_pro/.rubocop.yml

@@ -2,7 +2,6 @@
 inherit_from: ../.rubocop.yml
 
 AllCops:
-  EnableNewCops: true
   Exclude:
   <% `git status --ignored --porcelain`.lines.grep(/^!! /).each do |path| %>
     - <%= path.sub(/^!! /, '') %>