Build with JDK 8

(was: 21, breaking the bytebuddy version used in tests).

Author: post-svejk

.github/workflows/build.yml

@@ -31,7 +31,7 @@ jobs:
         uses: actions/setup-java@c5195efecf7bdfc987ee8bae7a71cb8b11521c00 # v4.7.1
         with:
           distribution: temurin
-          java-version: '21'
+          java-version: '8'
           cache: "maven"
           gpg-private-key: ${{ secrets.MAVEN_CENTRAL_SIGNING_KEY_PRIVATE }}
           server-id: central