reenable gkeconnect in quickstart ci builds

gkeconnect needs a release cycle to switch from using grpc connection headers to rest connection heads in the quickstart builds that rely on previous releases on google-cloud-cpp

Start by locating the quickstart CI build configurations and references to gkeconnect. Read how these builds depend on previous google-cloud-cpp releases and determine what release-cycle change is required for the REST connection headers. Done means gkeconnect is reenabled and the affected quickstart builds pass.

Written by the indexing model from the issue text.