Add ruby 2.6.2, remove ruby 2.6.0
Add ruby 2.6.2, remove ruby 2.6.0

for stack(s) cflinuxfs2, cflinuxfs3 [#164607809]

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