community/discount: remove checkdepends on diffutils

Discount 2.2.7b uses diff(1) only with BusyBox compatible options.

community/discount/APKBUILD

@@ -8,7 +8,6 @@ url="http://www.pell.portland.or.us/~orc/Code/discount/"
 arch="all"
 license="BSD-3-Clause"
 depends="!markdown"
-checkdepends="diffutils"
 subpackages="$pkgname-dev $pkgname-doc $pkgname-libs"
 source="$pkgname-$pkgver.tar.gz::https://github.com/Orc/discount/archive/v$pkgver.tar.gz
 	configure.inc.patch