firefox-bin/update: hard-code Mozilla's pubkey

Mozilla has ended the gpg.mozilla.org SKS server and the key can't be imported
from keys.openpgp.org because it lacks a user ID because Mozilla hasn't verified
their email...

Since the key isn't going to change any time soon and SKS is mostly busted,
might as well hard-code it.

pkgs/applications/networking/browsers/firefox-bin/update.nix

@@ -25,7 +25,8 @@ in writeScript "update-${name}" ''
 
   HOME=`mktemp -d`
   export GNUPGHOME=`mktemp -d`
-  gpg --keyserver hkps://gpg.mozilla.org --recv-keys 14F26682D0916CDD81E37B6D61B7B526D98F0353
+
+  gpg --import ${./mozilla.asc}
 
   tmpfile=`mktemp`
   url=${baseUrl}