ci.yml: Java 8 -> Java11

Author: mkarg

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java: [ '8' ]
+        java: [ '11' ]
         maven: [ '3.6.3', '3.8.8', '3.9.6' ]
     steps:
     - uses: actions/checkout@v4