[partition] Fix build for old Qt

src/modules/partition/jobs/ClearMountsJob.cpp

@@ -194,7 +194,12 @@ getPVGroups( const QString& deviceName )
 
                 vgSet.insert( vgName );
             }
+// toList() was deprecated, but old-old versions don't support QStringList construction like this
+#if QT_VERSION < QT_VERSION_CHECK( 5, 15, 0 )
+            return vgSet.toList();
+#else
             return QStringList { vgSet.cbegin(), vgSet.cend() };
+#endif
         }
     }
     else