Doc: Q_FLAG should be applied to the enum, not the QFlags

moc extracts he name that is inthe Q_FLAG macro and that gets used in
qDebug(). As the documentation described, qDebug would have printed:

  QFlags<LoadHints>(QLibrary::ResolveAllSymbolsHint)

which doesn't compile (though we could have partially specialized
QFlags<QFlags<E>> to be QFlags<E>). The semantically correct output is:

  QFlags<LoadHint>(QLibrary::ResolveAllSymbolsHint)

which is what this change gets. The ideal output would be:

  LoadHints(QLibrary::ResolveAllSymbolsHint)

But that's not a doc change.

Fixes: QTBUG-77216
Change-Id: I0635172f4f2a4c51a435fffd15b59a859886e90c
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/doc/snippets/code/src_corelib_kernel_qobject.cpp

@@ -416,7 +416,7 @@ public:
         LoadArchiveMemberHint = 0x04
     };
     Q_DECLARE_FLAGS(LoadHints, LoadHint)
-    Q_FLAG(LoadHints)
+    Q_FLAG(LoadHint)
     ...
 }
 //! [39]