Fix call to MemoryIntrospector in IndexerControllerContext. (#17066)

This was a logical conflict between #17057 and #17048.

extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/indexing/IndexerControllerContext.java

@@ -206,7 +206,7 @@ public int defaultTargetPartitionsPerWorker()
   {
     // Assume tasks are symmetric: workers have the same number of processors available as a controller.
     // Create one partition per processor per task, for maximum parallelism.
-    return memoryIntrospector.numProcessorsInJvm();
+    return memoryIntrospector.numProcessingThreads();
   }
 
   /**