Documentation: tracing: fix grammar

4a88d44ab17da ("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: Rabin Vincent <rabin@rab.in>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/trace/ftrace.txt

@@ -108,8 +108,8 @@ of ftrace. Here is a list of some of the key files:
 	data is read from this file, it is consumed, and
 	will not be read again with a sequential read. The
 	"trace" file is static, and if the tracer is not
-	adding more data,they will display the same
-	information every time they are read.
+	adding more data, it will display the same
+	information every time it is read.
 
   trace_options: