QDateTime: Fix time format in doc

MM stands for month, SS is invalid

Task-number: QTBUG-12236
Change-Id: I9b4a57d05d77fd38db30b53b16c382ea545edb80
(cherry picked from qtbase/a457bf3ff73627aa2c95f0482a838b14fd3233a0)
Reviewed-by: Thiago Macieira <[email protected]>

Author: orgads

src/corelib/tools/qdatetime.cpp

@@ -1533,7 +1533,7 @@ int QTime::msec() const
     Returns the time as a string. Milliseconds are not included. The
     \a format parameter determines the format of the string.
 
-    If \a format is Qt::TextDate, the string format is HH:MM:SS; e.g. 1
+    If \a format is Qt::TextDate, the string format is HH:mm:ss; e.g. 1
     second before midnight would be "23:59:59".
 
     If \a format is Qt::ISODate, the string format corresponds to the