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: I68cc5e8191bd8ef139aad220fad9f1ce3275bcbd
Addresses: blueprint rubocop-integer