remove package: unstable-repo

https://bintray.com/xeffyr/unstable-packages-21 is going to be disabled
after 01.01.2020.

packages/unstable-repo/build.sh

@@ -1,20 +0,0 @@
-TERMUX_PKG_HOMEPAGE=https://github.com/termux/unstable-packages
-TERMUX_PKG_DESCRIPTION="Package repository containing new/unstable programs and libraries."
-TERMUX_PKG_LICENSE="Apache-2.0"
-TERMUX_PKG_MAINTAINER="Leonid Plyushch <leonid.plyushch@gmail.com>"
-TERMUX_PKG_VERSION=1.1
-TERMUX_PKG_DEPENDS="termux-keyring"
-TERMUX_PKG_SKIP_SRC_EXTRACT=true
-TERMUX_PKG_PLATFORM_INDEPENDENT=true
-
-termux_step_make_install() {
-	mkdir -p $TERMUX_PREFIX/etc/apt/sources.list.d
-	echo "deb https://dl.bintray.com/xeffyr/unstable-packages-21 unstable main" > $TERMUX_PREFIX/etc/apt/sources.list.d/unstable.list
-}
-
-termux_step_create_debscripts() {
-	echo "#!$TERMUX_PREFIX/bin/sh" > postinst
-	echo "echo Downloading updated package list ..." >> postinst
-	echo "apt update" >> postinst
-	echo "exit 0" >> postinst
-}