fio:modify a deprecated parameter(change timeout to runtime)

since "timeout" had been deprecated long long ago, we should replace
to "runtime" both in code and docs

Signed-off-by: Liang Xie <xieliang@xiaomi.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fio.1 b/fio.1
index 5b61e43..086cf9d 100644
--- a/fio.1
+++ b/fio.1
@@ -20,8 +20,8 @@
 .BI \-\-output \fR=\fPfilename
 Write output to \fIfilename\fR.
 .TP
-.BI \-\-timeout \fR=\fPtimeout
-Limit run time to \fItimeout\fR seconds.
+.BI \-\-runtime \fR=\fPruntime
+Limit run time to \fIruntime\fR seconds.
 .TP
 .B \-\-latency\-log
 Generate per-job latency logs.