main/postmarketos-ondev: upgrade to 0.8.1 (MR 3280)

(cherry picked from commit aa996d27)

main/postmarketos-ondev/APKBUILD

 # Maintainer: Oliver Smith <ollieparanoid@postmarketos.org>
 pkgname=postmarketos-ondev
-pkgver=0.7.4
-pkgrel=1
+pkgver=0.8.1
+pkgrel=0
 pkgdesc="Calamares based on-device installer"
 url="https://postmarketos.org"
 # armhf blocked by qt5-qtdeclarative
@@ -48,5 +48,5 @@ package() {
 }
 
 sha512sums="
-57abb9c22a9eddf6369dcb96b5a86e518d3f10396b622b5358e718eec898fff1c133f30bb55471d0615eaa69b835679dbece336221f3ea17f5cef5a7a904bd9c  postmarketos-ondev-0.7.4.tar.gz
+259c1d771edf4722b3ef2959c0cb381e684f7db54079012d7ed76e389f7671106c7c5cea27e9e33c2fbd8bcac1cded9c43913639c98772465648df505c5495c3  postmarketos-ondev-0.8.1.tar.gz
 "