QWaitCondition: remove a misleading comment

The comment seems to imply that POSIX "does not allow for spurious
wakeups" on a pthread_cond_t, or that it doesn't allow for them to
happen on certain conditions. That's a misleading generalization. POSIX
allows for spurious wakeups [1], so we must handle them, end of story.

[1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_cond_timedwait.html

Task-number: QTBUG-109364
Change-Id: Iffcfbd85ec84c4e94a051f235fd3b3557a3aea9c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/thread/qwaitcondition_unix.cpp

@@ -111,9 +111,7 @@ public:
                 code = pthread_cond_wait(&cond, &mutex);
             }
             if (code == 0 && wakeups == 0) {
-                // many vendors warn of spurious wakeups from
-                // pthread_cond_wait(), especially after signal delivery,
-                // even though POSIX doesn't allow for it... sigh
+                // spurious wakeup
                 continue;
             }
             break;