gpg: Ignore all SHA-1 signatures in 3rd party key signatures.

* g10/sig-check.c (check_signature_over_key_or_uid): No cut-off date
and remove debug output.

With 2.2 we do not not support SHA-1 key signatures anymore even if
that means that the WoT shrinks.

• Signed-off-by: Werner Koch <wk@gnupg.org>