Remove stale comment in Gemfile
Remove stale comment in Gemfile

The comment was added in a91a6491bf3e74791ecf8dd1111d54435b8578cb, and referred to the below gem `grape-entity` being pulled directly from a Git repo. The `gem` command has already been changed to pull directly from Rubygems, so the comment is no longer necessary.

8thcolor/rubyconfau2015-sadr,8thcolor/rubyconfau2015-sadr,8thcolor/eurucamp2014-htdsadr,8thcolor/rubyconfau2015-sadr,8thcolor/eurucamp2014-htdsadr,8thcolor/eurucamp2014-htdsadr