rtla: Fix systme -> system typo on man page

Link: https://lkml.kernel.org/r/YhZsZxqk+IaFxorj@kernel.org

Fixes: 496082df

 ("rtla: Add rtla osnoise man page")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>