main/postmarketos-artwork: fix deprecated imagemagick call (MR 6084)

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

main/postmarketos-artwork/APKBUILD

 # Maintainer: Oliver Smith <ollieparanoid@postmarketos.org>
 pkgname=postmarketos-artwork
 pkgver=24.12
-pkgrel=1
+pkgrel=2
 pkgdesc="Meta package for the postmarketOS artwork"
 url="https://postmarketos.org/"
 arch="noarch"
@@ -53,7 +53,7 @@ wallpapers() {
 
 	# /usr/share/wallpapers/postmarketos.jpg should always point to the
 	# current wallpaper so we don't break configs
-	convert "$subpkgdir"/usr/share/wallpapers/postmarketos/contents/images/1660x1660.png \
+	magick convert "$subpkgdir"/usr/share/wallpapers/postmarketos/contents/images/1660x1660.png \
 		-format jpeg \
 		"$subpkgdir"/usr/share/wallpapers/postmarketos.jpg
 }