Separate branch for v3 pull requests

Author: mnapoli

.github/workflows/update-layer-versions.yml

@@ -60,6 +60,6 @@ jobs:
                         After merging, a new Bref release needs to be created.
                         
                         If you are using AWS Lambda layer ARNs, check out [runtimes.bref.sh](https://runtimes.bref.sh/) to see the latest ARNs.
-                    branch: new-layer-versions
+                    branch: new-layer-versions-v3
                     base: v3 # temporary until v3 becomes the main branch
                     delete-branch: true # delete after merging or closing the PR