Fixed a small typo in man/man1/raidz_test.1

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Peter Wirdemo <peter.wirdemo@gmail.com>
Closes #8855

man/man1/raidz_test.1

@@ -25,7 +25,7 @@
 .TH raidz_test 1 "2016" "ZFS on Linux" "User Commands"
 
 .SH NAME
-\fBraidz_test\fR \- raidz implementation verification and bencmarking tool
+\fBraidz_test\fR \- raidz implementation verification and benchmarking tool
 .SH SYNOPSIS
 .LP
 .BI "raidz_test <options>"