Removed Buffer from list

Buffer's website does not have a public section that reflects what a Handbook typical does, with specific policies and guidelines, thus it is removed.

README.md

@@ -7,7 +7,6 @@ A collection of open culture company handbooks
 | Armory | http://go.Armory.io/iterate |
 | Basecamp | https://github.com/basecamp/handbook |
 | Bonusly | https://github.com/bonusly/un-handbook |
-| Buffer | https://buffer.com/about |
 | GitLab | https://about.gitlab.com/handbook/ |
 | Nylas | https://github.com/nylas/handbook |
 | Sourcegraph |  https://about.sourcegraph.com/handbook |