Add rubygems 3.1.3, remove rubygems 3.1.2
Add rubygems 3.1.3, remove rubygems 3.1.2

for stack(s) cflinuxfs3 [#172663146]

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