fix: update release workflow to use Java 11

The Shadow plugin version 8.3.9 has dependencies compiled with Java 11
(class file version 55.0), but the release workflow was using Java 8
which only supports up to class file version 52.0.

Fixes #235

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

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

Author: korniltsev-grafanista

.github/workflows/release.yml

@@ -47,10 +47,10 @@ jobs:
           token: ${{ steps.app-token.outputs.token }}
           persist-credentials: true # push the tag later
 
-      - name: Set up Java 8
+      - name: Set up Java 11
         uses: actions/setup-java@c5195efecf7bdfc987ee8bae7a71cb8b11521c00 # v4
         with:
-          java-version: '8'
+          java-version: '11'
           distribution: 'temurin'
 
       - name: Bump Version