system/unzip: fix/update source URL with stable snapshot

system/unzip/APKBUILD

@@ -12,8 +12,9 @@ arch="all"
 license="Info-ZIP"
 subpackages="$pkgname-doc"
 # normally     ftp://ftp.info-zip.org/pub/infozip/src/$pkgname$_pkgver.zip
+# find timestamp here: https://snapshot.debian.org/package/unzip/
 source="$pkgname-$pkgver.tgz::https://distfiles.adelielinux.org/source/$pkgname$_pkgver.tgz
-	http://deb.debian.org/debian/pool/main/u/unzip/unzip_$pkgver-$_debver.debian.tar.xz
+	https://snapshot.debian.org/archive/debian-debug/20190928T162431Z/pool/main/u/$pkgname/$pkgname_$pkgver-$_debver.debian.tar.xz
 	cflags.patch
 	format-secure.patch
 	unzipsfx-bomb-32bit.patch