Disable the NumericLiterals cop for rubocop

- Disable the NumericLiterals cop in the .rubocop.yml file - this cop enforces
  an underscore '_' every 3 characters of an integer. This doesn't make much
  sense in our use case and reduces readability. Especially for port numbers.

Change-Id: I58447925ac7a05fb6848c31ac67285131fb8c872
Addresses: blueprint rubocop-integer