main/postmarketos-bootsplash: fix kill-pbsplash systemd service (MR 5286)

This wasn't actually getting run on boot because After=graphical.target
created an ordering issue and systemd was disabling it.

I saw this ordering issue in the journal after finding that pbsplash was
still running in the background after the UI loaded, and confirmed it by
running systemd-analyze.

main/postmarketos-bootsplash/APKBUILD

 # Maintainer: Caleb Connolly <caleb@connolly.tech>
 pkgname=postmarketos-bootsplash
-pkgver=0.2.2
+pkgver=0.2.3
 pkgrel=0
 pkgdesc="pmOS integration components for pbsplash"
 url="https://postmarketos.org"
@@ -61,7 +61,7 @@ systemd() {
 
 sha512sums="
 7e5416f0f9de3605dcbc5ddd4b93d244fd6d4fd1bc2d5a15a034263f8517fc51e73509f29f2a13397d059913917990ada89b36ac7b00a0d21c0283fade755c1c  kill-pbsplash
-9501b82c1da0495469dfd8daf3ab4c8b3cf4e818906d76b225ebd6e8ea2c2171c7834c3ba521e980b9cedc12955e4a22bc3bfbee73fb7cf6305c920aaa6afa53  kill-pbsplash.service
+79dd5eacf5914fb5eb1ef1b820478c07d2e0ae49441c9dc32c2ec18f26303f0e97c85221bab8e79abb854949e1ac4c20c566bb16379d4d396bda10d3d3b3d4d1  kill-pbsplash.service
 476c7a8106429c35e772eaf98e257f7a77070050431875113c7c0c75a358250757a381086c7302f1eded0d4cde88d2e63f9fa5d69b6fce46e2d908afd8d9323a  shutdown-splash.service
 c413607e21c805fff3d9948963aebf1048cdb2e68ed2f4316723d21f861a32aede7d1bf3851c8ba7562b07302471ca6d8f7be1e0487d83dd4cdea9bbb506e792  kill-pbsplash-override.conf
 3b862e2282c79d6ffc7aa8dc3992562c11fea5633c98e3ff9c6205a907f5d995e9fcf098adcf294e0648436df97746a3943b9b761ddf72339cc5589fb8904a8d  99-shutdown-pbsplash.stop

main/postmarketos-bootsplash/kill-pbsplash.service

 [Unit]
 Description=Stop pbsplash
-After=graphical.target
 Requisite=graphical.target
 
 [Service]