Release: Kogito Examples and Optaplanner Quickstarts `stable` branch should be created only when Maven artifacts are on Central

Right now, kogito-examples and optaplanner-quickstarts stable branches are set in the release pipeline just after the artifacts are released from Nexus.

Problem is that it can take up to 24 hours for the artifacts to be available on Maven Central.
So the stable may not work during almost a day.

We should update the stable branch only when artifacts are on Central, so 24 hours later.

Note: Optaplanner-website should be updated as well only when artifacts are on Central.