QSettings: fix a misleading comment

Destructors in C++ are implicitly noexcept, so the try-catch around
QSettingsPrivate::flush() is not to prevent throwing from a dtor
(anymore), but to prevent a throw statement inside flush() from taking
down the whole application.

We don't need to care about abi::__forced_unwind here, since we
couldn't re-throw it even if we wanted to (throw in noexcept function
is direct std::terminate(); at least by not re-throwing, the user will
get a nice complaint message from the runtime).

Pick-to: 6.3
Change-Id: I3b24a4be9aeb74637a58725540990b535d005bdd
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qsettings.cpp

@@ -2716,10 +2716,11 @@ QSettings::~QSettings()
 {
     Q_D(QSettings);
     if (d->pendingChanges) {
+        // Don't cause a failing flush() to std::terminate() the whole
+        // application - dtors are implicitly noexcept!
         QT_TRY {
             d->flush();
         } QT_CATCH(...) {
-            ; // ok. then don't flush but at least don't throw in the destructor
         }
     }
 }