Fix filename.

Thanks to @drebs for spotting this one.

COPYRIGHT

@@ -7,7 +7,7 @@ by Arnold G. Reinhold (files ``wordlists/wordlist_en_orig.asc``,
 license (see http://creativecommons.org/licenses/by/3.0/).
 
 The Securedrop wordlist (file
-``wordlists/wordlist_en_securedrop.txt``) by Heartsucker is licensed
+``wordlists/wordlist_en_securedrop.asc``) by Heartsucker is licensed
 under the `MIT` license (see http://mit-license.org/).
 
 The EFF wordlist (file ``wordlsts/wordlist_en_eff.txt``) is licensed