deps(ci): bump gradle/actions from 5 to 6

Bumps [gradle/actions](https://github.com/gradle/actions) from 5 to 6.
- [Release notes](https://github.com/gradle/actions/releases)
- [Commits](https://github.com/gradle/actions/compare/v5...v6)

---
updated-dependencies:
- dependency-name: gradle/actions
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/release.yml

@@ -117,7 +117,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Setup Gradle
-        uses: gradle/actions/setup-gradle@v5
+        uses: gradle/actions/setup-gradle@v6
 
       - name: Build
         run: ./gradlew :komga:prepareThymeLeaf :komga:bootJar :komga-tray:jar

.github/workflows/tests.yml

@@ -28,7 +28,7 @@ jobs:
           distribution: 'temurin'
 
       - name: Setup Gradle
-        uses: gradle/actions/setup-gradle@v5
+        uses: gradle/actions/setup-gradle@v6
 
       - name: Build
         run: ./gradlew build :komga-tray:jar