dependencies: remove unused lzma checking scripts

Files package/lzma/lzmacheck.sh and toolchain/dependencies/check-host-lzma.sh
are present since the very beginning of buildroot, but do not appear to be
used (anymore). Let's remove them.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>