g10: Rename 'card-edit' to 'edit-card'.

* g10/gpg.c (opts): Rename option.
* g10/call-agent.c (agent_scd_learn): Update comment.
* doc/gpg.texi: Update accordingly.

This change has a surprising side effect. Previously, --edit was an
alias for --edit-key, because the argument parser actually accepts
unique prefixes of all options. With this change, however, --edit is
ambiguous.

• GnuPG-bug-id: T2700
• Signed-off-by: Justus Winter <justus@g10code.com>