workflows: Run tuf-conformance in parallel

This should be just fine?

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

Author: jku

.github/workflows/tuf-conformance.yml

@@ -12,7 +12,6 @@ on:
 jobs:
   conformance:
     strategy:
-      max-parallel: 1
       matrix:
         java-version: [11, 17, 21]
       fail-fast: false