Add bundler 2.3.6, remove bundler 2.3.5
Add bundler 2.3.6, remove bundler 2.3.5

for stack(s) cflinuxfs3 [#181043947]

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