Update shellcheck.yml

(cherry picked from commit 6a31ef5)

.github/workflows/shellcheck.yml

@@ -18,7 +18,7 @@ jobs:
     name: runner / shellcheck
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v3
       - name: shellcheck
         # Make sure the action is pinned to a commit, as all reviewdog repos
         # have hundreds of contributors with write access (breaks easy/often)