Merge "cherrypick from mnc-io-docs docs: Updated Billing API documentation (for Project Nickel)." into mnc-io-docs am: 296d84fbd9
am: 59ce20df8c

* commit '59ce20df8c6573a149461943963e98cee3b11d72':
  cherrypick from mnc-io-docs docs: Updated Billing API documentation (for Project Nickel).

Change-Id: Iad0a2bc7ed5554b65e833f8ecb2936ffe4fb4b80