docs(INSTALL): inform users about `qtox-alpha` package

Also remove outdated info about generic binaries.

INSTALL.md

@@ -2,7 +2,6 @@
 - [Dependencies](#dependencies)
 - [Linux](#linux)
   - [Simple install](#simple-install)
-    - [Generic](#generic)
     - [Arch](#arch-easy)
     - [Gentoo](#gentoo-easy)
     - [Slackware](#slackware-easy)
@@ -57,7 +56,6 @@
 ### Simple install
 Easy qTox install is provided for variety of distributions:
 
-* [Generic](#generic)
 * [Arch](#arch)
 * [Gentoo](#gentoo)
 * [Slackware](#slackware)
@@ -71,13 +69,8 @@ Link | Distros | Architecture
 [OBS] | Arch, CentOS, Debian, Fedora, openSUSE, Ubuntu | x86, x86_64
 [Ubuntu PPA] | Ubuntu | arm64, armhf, ppc64el
 
-
-#### Generic
-There are available generic binaries for Linux:
-* [**64 bit download**](https://build.tox.chat/view/Clients/job/qTox_build_linux_x86-64_release/lastSuccessfulBuild/artifact/qTox_build_linux_x86-64_release.tar.xz)
-* [**32 bit download**](https://build.tox.chat/view/Clients/job/qTox_build_linux_x86_release/lastSuccessfulBuild/artifact/qTox_build_linux_x86_release.tar.xz)
-* [**Armhf download**](https://build.tox.chat/job/qTox-qt5.4.2_build_linux_armhf_release/lastSuccessfulBuild/artifact/qTox-qt5.4.2_build_linux_armhf_release.tar.xz)
-
+For release version, install `qtox`. To get latest changes, install
+`qtox-alpha`.
 
 ====