Update GitHub Actions to v4

Upgrade checkout, setup-java, and upload-artifact actions from v3 to v4
to fix deprecation warnings.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: mimno

.github/workflows/maven-publish.yml

@@ -18,10 +18,10 @@ jobs:
       packages: write
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up JDK 17
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           java-version: '17'
           distribution: 'temurin'
@@ -30,7 +30,7 @@ jobs:
         run: mvn --batch-mode verify
 
       - name: Upload Test Results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: always()
         with:
           name: test-results