gpg: Do not allow to accidently set the RENC usage.
* g10/keygen.c (print_key_flags): Print "RENC" if set. (ask_key_flags_with_mask): Remove RENC from the possible set of usages. Add a direct way to set it iff the key is encryption capable.
This could be done by using "set your own capabilities" for an RSA
key. In fact it was always set in this case.
- GnuPG-bug-id: T7072