Fix typo in docs README.
Fix typo in docs README.

[#111830633]

concourse/concourse,concourse/concourse,zachgersh/concourse,concourse/concourse,cjcjameson/concourse,cjcjameson/concourse,concourse/concourse,concourse/concourse,zachgersh/concourse,cjcjameson/concourse,zachgersh/concourse