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: I4e7f7c03efc501857afb4c5ecd7af1bba107a8c7
Addresses: blueprint rubocop-integer