Bump github/combine-prs from 3.1.2 to 4.0.0

Bumps [github/combine-prs](https://github.com/github/combine-prs) from 3.1.2 to 4.0.0.
- [Release notes](https://github.com/github/combine-prs/releases)
- [Commits](github/combine-prs@v3.1.2...v4.0.0)

---
updated-dependencies:
- dependency-name: github/combine-prs
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/combine-prs.yml

@@ -13,6 +13,6 @@ jobs:
     steps:
       - name: combine-prs
         id: combine-prs
-        uses: github/combine-prs@v3.1.2
+        uses: github/combine-prs@v4.0.0
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}