gnupg2: updated to 2.2.6

Noteworthy changes in version 2.2.6:
* gpg,gpgsm: New option --request-origin to pretend requests coming
  from a browser or a remote site.
* gpg: Fix race condition on trustdb.gpg updates due to too early
  released lock.
* gpg: Emit FAILURE status lines in almost all cases.
* gpg: Implement --dry-run for --passwd to make checking a key's
  passphrase straightforward.
* gpg: Make sure to only accept a certification capable key for key
  signatures.
* gpg: Better user interaction in --card-edit for the factory-reset
  sub-command.
* gpg: Improve changing key attributes in --card-edit by adding an
  explicit "key-attr" sub-command.
* gpg: Print the keygrips in the --card-status.
* scd: Support KDF DO setup.
* scd: Fix some issues with PC/SC on Windows.
* scd: Fix suspend/resume handling in the CCID driver.
* agent: Evict cached passphrases also via a timer.
* agent: Use separate passphrase caches depending on the request
  origin.
* ssh: Support signature flags.
* dirmngr: Handle failures related to missing IPv6 support
  gracefully.
* Fix corner cases related to specified home directory with
  drive letter on Windows.
* Allow the use of UNC directory names as homedir.

(adam)