unpinned dependencies in actions

Author: gcanlin

.github/workflows/rebase.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
-      - uses: ljharb/rebase@3f30d8c115145dcc562f01582f59fbeefe77c707 # master
+      - uses: actions/[email protected]
+      - uses: ljharb/rebase@master
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}