textproc/expat2: Update to 2.2.10

• give maintainership to desktop@
• add test target

Changelog:
https://github.com/libexpat/libexpat/blob/R_2_2_10/expat/Changes

PR: 243228
Submitted by: daniel.engberg.lists@pyret.net
Exp-run by: antoine
Approved by: Sergei Vyshenski <svysh.fbsd@gmail.com> (previous maintainer)