fixed a typo in the manpage (#476)

Signed-off-by: Srikanth Anantharam <sria91@gmail.com>

man/mosquitto_passwd.1.xml

@@ -41,7 +41,7 @@
 	<refsect1>
 		<title>Description</title>
 		<para><command>mosquitto_passwd</command> is a tool for managing
-			password files the mosquitto MQTT broker.</para>
+			password files for the mosquitto MQTT broker.</para>
 		<para>Usernames must not contain ":". Passwords are stored in a similar
 			format to
 			<citerefentry><refentrytitle>crypt</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>