gpg: Don't bail out for unknown subkey packet versions.

* g10/import.c (read_block): Don't show a warning for unbnown version
also for non-primary-key packets.
* g10/parse-packet.c (parse_key): Use log_info for unsupported v5
packets.

This fixes the problem that 2.2 can't import keys with a v5 subkey.
This fix allows a gnupg 2.6. version to export a key with an
additional PQC subkey and 2.2 can still import the other subkeys.

The second patch avoids that gpg returns with an error code.

Updates-commit: de70a2f377c1647417fb8a2b6476c3744a901296