systemd/postmarketos-base-systemd: pin polkit to our downstream (MR 5940) (MR 5563)

This is done in the usual way with a version requirement.

[ci:skip-build]: already built successfully in CI

extra-repos/systemd/postmarketos-base-systemd/APKBUILD

 # Maintainer: Oliver Smith <ollipearanoid@postmarketos.org>
 # pmbootstrap installs this, if systemd is selected in "pmbootstrap init".
 pkgname=postmarketos-base-systemd
-pkgver=10
+pkgver=11
 pkgrel=0
 pkgdesc="Meta package for running postmarketOS with systemd"
 url="https://postmarketos.org"
@@ -10,7 +10,7 @@ license="GPL-3.0-or-later"
 options="!check"
 depends="
 	openssh-server-pam
-	polkit
+	polkit>9990
 	systemd
 	systemd-timesyncd
 	tzdata