chore(docs): Remove from changelog some 1.9.0 features that were reverted

Closes #6867
Merge pull request #6928 from ewinslow/docs-changelog-reverted

chore(docs): Remove some 1.9.0 features that were reverted
fix(a11y): Label form fields in installer correctly

Refs #6743
fix(a11y): Use HTML5 form features on install forms

Email/Url fields are announced as such by screen readers
and prevent submission if not correctly formatted.

Required fields prevent submission of form if not filled in.
fix(a11y): Add semantic structure to installer page layout

aria landmark roles allow advanced screen reader users to
jump around the page quickly.

Aria roles are used in addition to semantic elements because
browsers do not yet consistently expose the semantic elements
as landmarks to assistive technology.

Ideally we would actually just shim this behavior with JS
so that we don't have to worry about consistently pairing
the elements with their equivalent roles.
Merge pull request #6924 from RiverVanRain/1.9

fix(replies): Show reply's link on river
Merge pull request #6931 from ewinslow/install-a11y

fix(install): Better accessibility for installation flow
Merge pull request #1 from Elgg/1.9

Elgg 1.9