chore: update GitHub Actions to support Node.js 24

Update action versions to support Node.js 24 before June 2nd, 2026 deadline:
- actions/checkout@v2 → v4 (Node.js 24 compatible)
- s4u/maven-settings-action@v3.0.0 → v3.1.0 (latest)

Resolves Node.js 20 deprecation warnings in workflow runs.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Flossy

.github/workflows/main.yml

@@ -23,10 +23,10 @@ jobs:
           java-version: '21'
 
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Preparing settings.xml
-        uses: s4u/maven-settings-action@v3.0.0
+        uses: s4u/maven-settings-action@v3.1.0
         with:
           githubServer: false
           servers: |