Add note that administrative public key for gitolite has to be written in one line

nixos/modules/services/misc/gitolite.nix

@@ -36,6 +36,7 @@ in
           Initial administrative public key for Gitolite. This should
           be an SSH Public Key. Note that this key will only be used
           once, upon the first initialization of the Gitolite user.
+          The Key has to be written in one line.
         '';
       };