Consider to remove some left overs from the old jQuery.suggest

[afercia]

Noticed while investigating on #40242. Core doesn't use jquery.suggest since [38797], however there are some left overs here and there that reference the ac_results class used for the jquery.suggest results.

The JavaScript part can be safely removed. The CSS part might still be used by some very old plugins so maybe better to keep it and add some inline comment.

See quick discussion on Slack:
​https://wordpress.slack.com/archives/C02QB2JS7/p1490370129805243

Aside: Maybe one more reason to add a deprecated.css somewhere, as this idea has been around since a while. See for example #21456, #26396, and also ​https://make.wordpress.org/core/2014/12/19/core-css-roadmap/

[afercia]

See also #27555 where the decision was to keep the CSS in core for backwards compatibility.

[Hareesh Pillai]

Patch refreshed

[Hareesh Pillai]

Refresh

[garrett-eclipse]

Clear up comment verbiage. New verbiage "Back-compat styles from deprecated jQuery.suggest, see ticket #40260."

[garrett-eclipse]

Quick refresh in 40260.3.diff to correct the comment language.

P.S. I'm all for a deprecated.css, I feel that's a great idea and for those wanting clean installs that know they don't use any of that css hopefully they can easily dequeue it.

[garrett-eclipse]

This is looking good as is just maybe getting someone other than myself to test the latest patch is enough to bring this to commit.

[SergeyBiryukov]

In 49213:

Administration: Remove obsolete .ac_results class references.

Core does not use the jQuery.suggest plugin since [38797].

Props afercia, hareesh-pillai, garrett-eclipse.
Fixes #40260.