HPCC-17536 Grouped Aggregate, incorrectly reporting grouped output

Signed-off-by: Jake Smith <jake.smith@lexisnexisrisk.com>

thorlcr/activities/aggregate/thgroupaggregateslave.cpp

@@ -73,13 +73,16 @@ public:
         dataLinkIncrement();
         return out.finalizeRowClear(sz);
     }
-
     virtual void getMetaInfo(ThorDataLinkMetaInfo &info) override
     {
         initMetaInfo(info);
         info.canReduceNumRows = true;
         info.fastThrough = true;
     }
+    virtual bool isGrouped() const override
+    {
+        return false;
+    }
 };