Update Mozilla gpg key

The build of tbb-8.5.4-build1 fails with the error:

Error: File SHA512SUMS-60.8.0esr-build1 is not signed with a valid key

We need to update the key in keyring/firefox.gpg to add the new subkey.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information