Convert to using a GH PAT token for release-plz to allow binary releases.

Author: tarka

.github/workflows/release-plz.yml

@@ -30,7 +30,7 @@ jobs:
         with:
           command: release
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.RELEASE_PLZ_TOKEN }}
 
   # Create a PR with the new versions and changelog, preparing the next release.
   release-plz-pr:
@@ -52,4 +52,4 @@ jobs:
         with:
           command: release-pr
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.RELEASE_PLZ_TOKEN }}