Add jruby 9.2.21.0, remove jruby 9.2.20.1
Add jruby 9.2.21.0, remove jruby 9.2.20.1

for stack(s) cflinuxfs3 [#182577073]

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