Make the side bar about in-document navigation by removing the duplicated h1

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Merge pull request #7949 from SvenDowideit/remove-doubled-up-page-heading

Make the side bar about in-document navigation by removing the duplicated h1