Sets Gemfile.lock to support bookbinder 9.12.0
Sets Gemfile.lock to support bookbinder 9.12.0

swisscom/docs-appcloud-book,cloudfoundry/docs-book-cloudfoundry,cloudfoundry/docs-book-cloudfoundry,cloudfoundry/docs-book-cloudfoundry,cloudfoundry/docs-book-cloudfoundry,swisscom/docs-appcloud-book,swisscom/docs-appcloud-book,swisscom/docs-appcloud-book