1. Sync sphinx dependency with global requirements. It caps python 2 since
sphinx 2.0 no longer supports Python 2.7.
2. Remove unncessary "=="
Change-Id: I3451c44a30a2e3d4bb58d2ac512e69da0781e961
Fix some typos that I found in documents(except specs)
* fix trivial mistakes(typos)
* fix the link error(rst->html)
* restore it's -> its
* fix k8s -> K8s
Change-Id: I6ec65e9d04441adac210cc9fd476a37a1cb9644f