installation: Fix a typo.

installation/20install-image.sh

@@ -14,7 +14,7 @@ get_partition_path () {
 	# Return the path of the desired partition.
 	# Exit and display an error if it finds 0 or several results.
 	#
-	# This function should be called ith exactly one argument: the desired partition type.
+	# This function should be called with exactly one argument: the desired partition type.
 	# Its behavior is undefined otherwise.
 
 	desired_partitions=$(fdisk -l | grep "$1")