tracing: Remove the useless value assignment in test_create_synth_event()

The value of variable ret is overwritten on the delete branch in the
test_create_synth_event() and we care more about the above error than
this delete portion. Remove it.

Link: https://lkml.kernel.org/r/1605283360-6804-1-git-send-email-kaixuxia@tencent.com



Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>