Remove redundant redundant remove

Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Giuseppe Di Natale <guss80@gmail.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Elling <Richard.Elling@RichardElling.com>
Closes #8839

tests/zfs-tests/include/libtest.shlib

@@ -939,7 +939,6 @@ function set_partition
 		rm -f $format_file
 	fi
 
-	rm -f $format_file
 	if [[ $ret_val -ne 0 ]]; then
 		log_note "Unable to format $disk slice $slicenum to $size"
 		return 1