Add rubygems 2.7.7, remove rubygems 2.7.6 [#157685124]
Add rubygems 2.7.7, remove rubygems 2.7.6 [#157685124]

cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack