deskutils/py-khard: Update 0.19.1 => 0.20.0, undeprecate, take maintainership

Changelog:

• Replace atomicwrites dependency with an inlined function

https://github.com/lucc/khard/blob/v0.20.0/CHANGES

While here fix warnings from portclippy, call mkdir once for 2 dirs.

PR: 288472