MAINT try debian 9

Author: davidmalloncares

.github/workflows/test-legacy-compilers.yaml

@@ -71,7 +71,7 @@ jobs:
             bundle exec bolt plan run peadm_spec::provision_test_cluster \
               --modulepath spec/fixtures/modules \
               provider=docker \
-              image=litmusimage/ubuntu:22.04 \
+              image=litmusimage/debian:9 \
               architecture=large-with-dr
           echo ::endgroup::
           echo ::output_directory::