cid#1507491 cut and paste typo triggering 'Constant' variable guards dead code

Change-Id: I9b833575f3cc3ba886b355eefdfa9155d2dffae1
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/137587
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
Tested-by: Jenkins

oox/source/export/chartexport.cxx

@@ -2053,7 +2053,7 @@ void ChartExport::exportDataTable( )
     if (GetProperty(aPropSet, "Outline"))
         mAny >>= bShowOutline;
     if (GetProperty(aPropSet, "Keys"))
-        mAny >>= bShowOutline;
+        mAny >>= bShowKeys;
 
     pFS->startElement(FSNS(XML_c, XML_dTable));