.github: fix codeql GH workflow to only run on push to branch 'master'
.github: fix codeql GH workflow to only run on push to branch 'master'

Fixes: b08f700aff5a ("workflows: Skip jobs instead of workflows")
Signed-off-by: André Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>

michi-covalent/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium