.github: update maven GitHub actions workflow

- Switch to Ubuntu 22.04 because `ubuntu-latest` is still 20.04
- Update actions to latest versions
- Specify Java 8 instead of 1.8
- Enable Maven caching

.github/workflows/maven.yml

@@ -12,13 +12,14 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up JDK 1.8
-      uses: actions/setup-java@v1
+    - uses: actions/checkout@v3
+    - name: Set up JDK 8
+      uses: actions/setup-java@v3
       with:
-        java-version: 1.8
+        java-version: 8
+        cache: 'maven'
     - name: Build with Maven
       run: mvn -B package --file pom.xml