system/unzip: fix license by making it SPDX

system/unzip/APKBUILD

@@ -8,7 +8,7 @@ pkgrel=3
 pkgdesc="Extract PKZIP-compatible .zip files"
 url="http://www.info-zip.org/UnZip.html"
 arch="all"
-license="custom"
+license="Info-ZIP"
 subpackages="$pkgname-doc"
 # normally     ftp://ftp.info-zip.org/pub/infozip/src/$pkgname$_pkgver.zip
 source="$pkgname-$pkgver.tgz::https://distfiles.adelielinux.org/source/$pkgname$_pkgver.tgz