Bump actions/upload-artifact from 2 to 4 (#111)

Author: dependabot[bot]

.github/workflows/maven.yml

@@ -16,7 +16,7 @@ jobs:
     - name: Build with Maven
       run: mvn -B package --file pom.xml
     - name: Upload artifact
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       with:
         # Artifact name
         name: NoteblockAPI