temp/plasma-nano: upgrade to 5.20.2_git20201001 (MR 1663)

plasma-nano (albeit saying it is 5.20.1) is pointing to the master branch
and kept as-is (there is no updates in master and I don't see a reason to
downgrade it to the actual 5.20.2 tag which is a few small commits behind
the master).

temp/plasma-nano/APKBUILD

 # Forked from Alpine to package newer commits
 pkgname=plasma-nano
-pkgver=5.20.1_git20201001
+pkgver=5.20.2_git20201001
 pkgrel=0
 _commit="6a456033bfa13cc57d28b2a49a8ac6615bc60439"
 pkgdesc="A minimal Plasma shell package intended for embedded devices"