docs: fix syntax in gluon-authorized-keys

docs/features/authorized-keys.rst

@@ -7,9 +7,9 @@ SSH public keys to an image to permit root login.
 If you select this package, add a list of authorized keys to ``site.conf`` like this:::
 
   {
-    authorized_keys: { 'ssh-rsa AAA.... user1@host',
-                       'ssh-rsa AAA.... user2@host }
-    hostname_prefix: ...
+    authorized_keys = { 'ssh-rsa AAA.... user1@host',
+                        'ssh-rsa AAA.... user2@host },
+    hostname_prefix = ...
     ...
 
 Existing keys in ``/etc/dropbear/authorized_keys`` will be preserved.