QBenchlib/Perf: remove ioctl(FD_CLOEXEC)

Commit 8995045c62 forgot to remove this
portion.

Pick-to: 6.4
Change-Id: I3c79b7e08fa346988dfefffd17202b19665ddc8a
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

src/testlib/qbenchmarkperfevents.cpp

@@ -487,8 +487,6 @@ void QBenchmarkPerfEventsMeasurer::start()
         if (fd == -1) {
             perror("QBenchmarkPerfEventsMeasurer::start: perf_event_open");
             exit(1);
-        } else {
-            ::fcntl(fd, F_SETFD, FD_CLOEXEC);
         }
     }