Specify an underlying type for QCommandLineParser::MessageType

And also add a trailing comma to the last element of the enum to
minimize future diffs.

Amends bad618606d64e943e3fa78e7d1dbc8e1fab55480.

Found in Qt 6.9 API review.

Change-Id: I1a30c344967005c9abc73e59980e56626e09cd7c
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 14cc2591ac06dbcee01c2b110e014db2993d7a1e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qcommandlineparser.h

@@ -67,9 +67,9 @@ public:
     Q_NORETURN void showHelp(int exitCode = 0);
     QString helpText() const;
 
-    enum MessageType {
+    enum MessageType : quint32 {
         InformationMessage,
-        ErrorMessage
+        ErrorMessage,
     };
     Q_NORETURN static void showMessageAndExit(const QString &message, MessageType type, int exitCode = 0);