GitLab

Drop unused manpages:

* d/xtables-compat.8 is no longer relevant, the information is included in xtables-nft.8
* d/xtables-translate.8 is already included in the upstream tarball
* d/xtables-multi.8 is no longer relevant, info in either xtables-{nft,legacy}-multi.8
Signed-off-by: Arturo Borrero Gonzalez <arturo@debian.org>