Revert "Diff headers made sticky."

This reverts commit 6eb85b1a30eb2e87fc6a55d17bb38fdf535a516b.
Merge branch 'revert_sticky_headers' into 'master'

Revert sticky headers

See merge request !1104
Version 7.3.0.
Update manual installation guide for the correct shell version.
Support sockets in 'rake gitlab:shell:install'
Merge branch 'shell_install_socket'

Conflicts:
	doc/install/installation.md