Bump GitHub Actions versions [skip ci]

Updated all GitHub Actions to latest versions:
- actions/checkout: v4 → v6
- actions/setup-java: v4 → v5

Versions aligned with latest releases:
- checkout@v6: Latest stable release
- setup-java@v5: Latest with node24 support

Author: kwent

.github/workflows/maven.yml

@@ -19,9 +19,9 @@ jobs:
       matrix:
         java: [ 17, 21 ]
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Set up JDK
-      uses: actions/setup-java@v4
+      uses: actions/setup-java@v5
       with:
         java-version: ${{ matrix.java }}
         distribution: 'temurin'

.github/workflows/publish.yml

@@ -9,9 +9,9 @@ jobs:
   test-and-publish:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up JDK
-        uses: actions/setup-java@v4
+        uses: actions/setup-java@v5
         with:
           java-version: '17'
           distribution: 'temurin'

.github/workflows/test.yml

@@ -9,9 +9,9 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up JDK
-        uses: actions/setup-java@v4
+        uses: actions/setup-java@v5
         with:
           java-version: '17'
           distribution: 'temurin'