Run "clean-keydir clean" over the active + emeritus keyrings, picking
up the new option that strips out UATs (which may contain copyright that
is non-free).

 32M ->  28M debian-keyring-gpg
4.8M -> 1.6M emeritus-keyring-gpg
3.9M -> 3.5M debian-maintainers-gpg
448k -> 428k debian-nonupload-gpg