Add ruby 2.5.5, remove ruby 2.5.4
Add ruby 2.5.5, remove ruby 2.5.4

for stack(s) cflinuxfs2, cflinuxfs3 [#164698728]

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