gpg: Fix memory leak in sig-check.

* g10/sig-check.c (check_signature_over_key_or_uid): Remove useless
condition.  Actually free when SIGNER was allocated by us.

SIGNER_ALLOCATED never received a value of -1 but that was tested.

IF SIGNER_ALLOCATED was 2 the memory was never freed:

if (signer_allocated == 1)
  if (signer_allocated == 2)
    free()

This function needs to be audited more thoroughly.

• Fixes-commit: 44cdb9d73f1a0b7d2c8483a119b9c4d6caabc1ec
• Signed-off-by: Werner Koch <wk@gnupg.org>