QMultiHash: use move() on key when move-constructing nodes

Change-Id: Ibc2bd1c2b11d3fa29814db0cae1caf0e2c23bb54
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qhash.h

@@ -173,7 +173,7 @@ struct MultiNode
     {}
 
     MultiNode(MultiNode &&other)
-        : key(other.key),
+        : key(std::move(other.key)),
           value(std::exchange(other.value, nullptr))
     {
     }