test(planner): call the promoted PromQL workload lowering

The PromQL frontend's unified module was promoted to the crate root later
in the stack; asap_frontend_promql::unified no longer exists.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: zzylol

crates/asap-aware-mapping/tests/logical_candidates.rs

@@ -179,7 +179,7 @@ fn promql_lowering_reaches_local_candidates_without_execution_timing() {
             ..Default::default()
         }),
     };
-    let roots = asap_frontend_promql::unified::lower_promql_query_workload(&workload, 0).unwrap();
+    let roots = asap_frontend_promql::lower_promql_query_workload(&workload, 0).unwrap();
     let candidates =
         enumerate_local_logical_candidates(roots.into_iter().enumerate().collect()).unwrap();
     assert!(candidates