GitHub Actions: update to github-script@v7

We seem to be getting "Node.js 16 actions are deprecated." warnings
for jobs that use github-script@v6.  Update to github-script@v7,
which is said to use Node.js 20.

Backported-from: c4ddbe043e (GitHub Actions: update to github-script@v7, 2024-02-02)
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

.github/workflows/main.yml

@@ -46,7 +46,7 @@ jobs:
           echo "skip_concurrent=$skip_concurrent" >>$GITHUB_OUTPUT
       - name: skip if the commit or tree was already tested
         id: skip-if-redundant
-        uses: actions/github-script@v6
+        uses: actions/github-script@v7
         if: steps.check-ref.outputs.enabled == 'yes'
         with:
           github-token: ${{secrets.GITHUB_TOKEN}}