4a88d44a ("tracing: Remove mentioning of legacy latency_trace file
from documentation") changed a sentence to refer to only one file
instead of two, but the sentence still uses "they".  Fix it.
Signed-off-by: NRabin Vincent <rabin@rab.in>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>