Add bundler 2.2.12, remove bundler 2.2.11
Add bundler 2.2.12, remove bundler 2.2.11

for stack(s) cflinuxfs3 [#177141686]

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