Typo fix in man page.

josn should be json, of course.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fio.1 b/fio.1
index b746da1..84d71a0 100644
--- a/fio.1
+++ b/fio.1
@@ -21,7 +21,7 @@
 Write output to \fIfilename\fR.
 .TP
 .BI \-\-output-format \fR=\fPformat
-Set the reporting format to \fInormal\fR, \fIterse\fR, or \fIjosn\fR.
+Set the reporting format to \fInormal\fR, \fIterse\fR, or \fIjson\fR.
 .TP
 .BI \-\-runtime \fR=\fPruntime
 Limit run time to \fIruntime\fR seconds.