main/postmarketos-ondev: upgrade to 0.2.1
After spending the whole day on it, finally a reliable workaround for the very annoying virtual keyboard bug postmarketos-ondev#18 (closed)!
I've verified 10x that this boots on the pinephone without getting the bug.
Related: https://gitlab.com/postmarketOS/postmarketos-ondev/-/tags/0.2.1