Correct the Zend\Version\Version::getLatest docblock

- Was incorrectly indicating that the github API is used by default;
  altered the docblock to indicate that the framework.zend.com API is
  used by default, and how to use the github API.

See https://github.com/zendframework/zf2/commit/8009f542a65901eec9a3133859ccd48f8b310677#commitcomment-3642835
CS fixes

- Trailing whitespace
Merge pull request #4847