Merge branch 'remove-1404-install-docs' into 'master'

Remove 14.04 LTS from installation docs

See merge request gitlab-com/www-gitlab-com!23219

source/install/index.html.haml

@@ -28,7 +28,7 @@ extra_js:
         - distros = ['Ubuntu', 'Debian', 'CentOS 6', 'CentOS 7', 'OpenSUSE 42.3', 'Raspberry Pi 2']
         - platforms = ['ubuntu', 'debian', 'centos6', 'centos7', 'opensuse', 'raspberrypi2']
         - ce_only_platforms = { 'raspberry-pi-2' => true }
-        - subtitles = ['14.04 LTS, 16.04 LTS, 18.04 LTS', '8, 9', 'and RHEL, Oracle, Scientific', 'and RHEL, Oracle, Scientific', 'and SUSE Linux Enterprise Server 12.2', 'Raspbian Stretch']
+        - subtitles = ['16.04 LTS, 18.04 LTS', '8, 9', 'and RHEL, Oracle, Scientific', 'and RHEL, Oracle, Scientific', 'and SUSE Linux Enterprise Server 12.2', 'Raspbian Stretch']
         - icons = ['ubuntu', 'debian', 'centos', 'centos', 'opensuse', 'raspberry-pi']
         .method-content
           %h2.block-title{id: "#omnibus"} Omnibus package installation (recommended)