tracing/filter: Remove synchronize_sched() from __alloc_preds()

Because the filters are processed first and then activated
(added to the call), we no longer need to worry about the preds
of the filter in __alloc_preds() being used. As the filter that
is allocating preds is not activated yet.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>