Update gitlab-shell in docs to 2.4.1 (stable)

Changes for 7.7.0.rc4

See merge request !1409

Conflicts:
	CHANGELOG

Changes from master into 7.7

There are list of changes it will be good to have in 7.7 release like comment improvements and fixes to CI on tags

See merge request !1402

Send checkout sha to services

In case of tags it may be useful to have sha of commit this tag points to.
So now web hooks and services get additional parameter `checkout_sha`

See merge request !1400

Remove password strength indicator

We were having the following issues:
- the indicator would sometimes stay red even if the password that was
  entered was long enough;
- the indicator had a middle yellow signal: what does that mean?
- the red/green backgrounds were not color-blind-friendly.

See merge request !1399

Fix tab index

Fixes #1892

See merge request !1401

Update the Omnibus package in Dockerfile

We were having the following issues:
- the indicator would sometimes stay red even if the password that was
  entered was long enough;
- the indicator had a middle yellow signal: what does that mean?
- the red/green backgrounds were not color-blind-friendly.

Fix comments

Fixes:

* drag-n-drop works for diff comments
* selecting images works for diff comments
* preview works for edit comments
* drag-n-drop works for edit comments
* selecting images works for edit comments
* if comment presented on 'Discussion' and 'Changes' tabs - after edit it updates on both tabs.
* Correctly hide form when edit comment on diff
* fix full-screen for diff comments

See merge request !1398

View link first

See merge request !1397

Fix scroll issue

Fixes #1886

See merge request !1396