[ci] Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

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

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

.github/workflows/maven.yml

@@ -23,13 +23,13 @@ jobs:
 
     steps:
       - name: Checkout core repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: debezium/debezium
           ref: main
           path: core
       - name: Checkout Debezium Operator
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: operator
       - name: Set up JDK

.github/workflows/sanity-check.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Commit messages in format DBZ-xxx
         env:
           BASE_REF: ${{ github.base_ref }}