firefox-unwrapped: Update GPG signing key

https://blog.mozilla.org/security/2023/05/11/updated-gpg-key-for-signing-firefox-releases/

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

···
   set -eux
   HOME=`mktemp -d`
   export GNUPGHOME=`mktemp -d`
-  gpg --receive-keys 14F26682D0916CDD81E37B6D61B7B526D98F0353
+  gpg --receive-keys ADD7079479700DCADFDD5337E36D3B13F3D93274
 
   url=${baseUrl}