tracing: Remove unneeded event_mutex lock in event_trigger_regex_release()

In event_trigger_regex_release(), the only code is:

mutex_lock(&event_mutex);
if (file->f_mode & FMODE_READ)
seq_release(inode, file);
mutex_unlock(&event_mutex);

return 0;

There's nothing special about the file->f_mode or the seq_release() that
requires any locking. Remove the unnecessary locks.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Link: https://patch.msgid.link/20251125214031.975879283@kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>