community/apache-mod-md: upgrade to 2.4.28

https://github.com/icing/mod_md/releases/tag/v2.4.28

community/apache-mod-md/APKBUILD

 # Contributor: Síle Ekaterin Liszka <sheila@vulpine.house>
 # Maintainer: Síle Ekaterin Liszka <sheila@vulpine.house>
 pkgname=apache-mod-md
-pkgver=2.4.27
+pkgver=2.4.28
 pkgrel=0
 pkgdesc="Integrated Acme protocol support for apache2"
 url="https://github.com/icing/mod_md"
@@ -43,5 +43,5 @@ package() {
 }
 
 sha512sums="
-5766c41971890bdd723c626c9684160eafa1352b34931f6ceb2a616e7c3ecfc044ffca5dbb98a6e58fd78618c28cd0520fc6127cf42a0bef68450b4310be1773  mod_md-2.4.27.tar.gz
+74ef7cae20237d8791f5402fa74711e4b157dcc63398f8c85904fd62fb14a17c736ccd778e10b5b608447a1d2c51095e7a4fd408f6c321a7f758e24b4f0f0356  mod_md-2.4.28.tar.gz
 "