mail/claws-mail*: Update 4.3.1 => 4.4.0, remove GTK2 option that use version 3.21.0

Release Notes:
https://lists.claws-mail.org/pipermail/users/2026-March/034710.html

• Remove option GTK2 - GTK2 supported in 3.x only, but 3.x reached EoL.
• Make cosmetic improvements and cleanups.

PR: 293704
Approved by: Chris Hutchinson <portmaster@bsdforge.com> (maintainer)
Co-authored-by: Polarian <polarian@polarian.dev>
Co-authored-by: Chris Hutchinson <portmaster@bsdforge.com>