CI: Attempt to get a JRuby test passing

This adds the JAVA_OPTS mentioned in a warning message, as well as asking for more memory.

.github/workflows/test.yml

@@ -35,6 +35,9 @@ jobs:
           vcpkg: libyaml
       - name: Install dependencies
         run: bundle install --jobs 1
+        env:
+          JAVA_OPTS: "--add-opens java.base/sun.nio.ch=ALL-UNNAMED --add-opens java.base/java.io=ALL-UNNAMED"
+          JRUBY_OPTS: "-J-Xmx1g"
       - name: Run test
         run: rake
       - name: Install gem