chore(deps): bump actions/setup-java from 3 to 4

Bumps [actions/setup-java](https://github.com/actions/setup-java) from 3 to 4.
- [Release notes](https://github.com/actions/setup-java/releases)
- [Commits](actions/setup-java@v3...v4)

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/backend.yml

@@ -20,7 +20,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Set up JDK
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           java-version: '21'
           distribution: 'adopt'
@@ -45,7 +45,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Set up JDK
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           java-version: '21'
           distribution: 'adopt'