Another load() -> loadRelaxed()

Change-Id: Iab74325da3bd0a22c1f69856b038d0b5615e4e63
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/gui/rhi/qshaderdescription.cpp

@@ -1022,7 +1022,7 @@ void QShaderDescriptionPrivate::loadDoc(const QJsonDocument &doc)
         return;
     }
 
-    Q_ASSERT(ref.load() == 1); // must be detached
+    Q_ASSERT(ref.loadRelaxed() == 1); // must be detached
 
     inVars.clear();
     outVars.clear();