Pin the full SHA (#17393)

Author: JasonEtco

.github/allowed-actions.js

@@ -33,7 +33,7 @@ module.exports = [
   'repo-sync/github-sync@3832fe8e2be32372e1b3970bbae8e7079edeec88',
   'repo-sync/pull-request@33777245b1aace1a58c87a29c90321aa7a74bd7d',
   'someimportantcompany/github-actions-slack-message@0b470c14b39da4260ed9e3f9a4f1298a74ccdefd',
-  'tjenkinson/gh-action-auto-merge-dependency-updates@cee2ac0',
+  'tjenkinson/gh-action-auto-merge-dependency-updates@4d7756c04d9d999c5968697a621b81c47f533d61',
   'EndBug/add-and-commit@9358097a71ad9fb9e2f9624c6098c89193d83575',
   'dorny/paths-filter@eb75a1edc117d3756a18ef89958ee59f9500ba58'
 ]

.github/workflows/automerge-dependencies.yml

@@ -17,7 +17,7 @@ jobs:
     if: github.repository == 'github/docs-internal' || github.repository == 'github/docs'
     runs-on: ubuntu-latest
     steps:
-      - uses: tjenkinson/gh-action-auto-merge-dependency-updates@cee2ac0
+      - uses: tjenkinson/gh-action-auto-merge-dependency-updates@4d7756c04d9d999c5968697a621b81c47f533d61
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           allowed-actors: dependabot[bot]