Update PV1 with the new branch information

For more information, refer to Creating release branches for RHBQ documentation procedure.

1. Open the Red Hat build of Quarkus product in Pantheon; go to the section for your release branch (e.g., “Red Hat build of Quarkus 3.8”);  for each guide, edit the Preview and Stage settings; and change the Branch from main to the new release branch.
2. IMPORTANT - Go back a few minutes later and check each of these Branch settings. In many cases, the initial change to the release branch fails. You must reapply until you have confirmed that it “sticks”. Don’t assume the change is complete until you have confirmed it.