Bump actions/checkout from 2 to 4 (#449)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/postgresql-14-build.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Clone postgres repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           repository: 'postgres/postgres'
           ref: 'REL_14_STABLE'
@@ -73,7 +73,7 @@ jobs:
           pg_ctl -D /opt/pgsql/data -l logfile start
 
       - name: Clone pg_stat_monitor repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           path: 'src/pg_stat_monitor'