`VagrantPlaybookCheck` cannot run CentOS6 with JDK21+ build

With JDK20 and later we moved to building on CentOS7 which means the boot JDK for JDK21 and later cannot be run on vagrantPlaybookCheck when using CentOS6 if a build of JDK21 and above is selected. We should modify [vagrantPlaybookCheck](https://github.com/adoptium/infrastructure/blob/master/ansible/pbTestScripts/vagrantPlaybookCheck.sh) so that if CentOS6 is selected with an inappropriate JDK build then we put out a warning message and skip the build.

Start with ansible/pbTestScripts/vagrantPlaybookCheck.sh and trace how the selected CentOS6 image and JDK build are handled. Verify the CentOS6/JDK21-or-later case, then confirm that it emits a warning and skips the build while valid combinations continue normally.

Written by the indexing model from the issue text.