Temporarily allow JRuby builds to fail

Ref. https://github.com/railsadminteam/rails_admin/actions/runs/9818319823/job/27110703992

.github/workflows/test.yml

@@ -68,6 +68,7 @@ jobs:
             adapter: sqlite3
             asset: sprockets
     runs-on: ubuntu-latest
+    continue-on-error: ${{ startsWith(matrix.ruby, 'jruby') }}
     services:
       mysql:
         image: mysql:8.0