QRecursiveMutex: remove QDeadlineTimer::Forever leftover

Amends 5f531ae2ac
The overload taking QDeadlineTimer::ForeverConstant was required,
prior to making it an enum class, because the conversion preferred
'int'. It was made an enum class for 6.6 and most overloads were
removed, including the one for QMutex, but QRecursiveMutex was
missed.

Pick-to: 6.6
Change-Id: I4490dd3d7641c06346ea502f10c09915411319ad
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/thread/qmutex.h

@@ -200,12 +200,6 @@ public:
     {
         return tryLock(QDeadlineTimer(timePoint));
     }
-
-#ifndef Q_QDOC
-    // because tryLock(QDeadlineTimer::Forever) is tryLock(0)
-    bool tryLock(QDeadlineTimer::ForeverConstant) QT_MUTEX_LOCK_NOEXCEPT
-    { lock(); return true; }
-#endif
 };
 
 #if QT_CORE_INLINE_IMPL_SINCE(6, 6)