Use the built-in utilities instead.

Also, add a warning in _root.scss so that we don't miss it again.

While important in the past, it has become obsolete, so removing it seems the best solution.

- Add example to the new form control docs
- Reset the [list] selector in Reboot to hide the random dropdown arrow in Chrome

* Follow-up to #29095

This PR fixes the responsive containers that were added in #29095, originally stubbed out in #25631. Apologies to @browner12 for getting that wrong.

Fixes #25631.

* update navbar as well because we cannot reset all containers uniformly

* Update navbars example to include container-xl example to ensure containers match

* rewrite responsive containers docs, add table of max-widths

* Update container docs
- Move table up to the intro
- Remove the container example because it's actually hella confusing
- Update and link to grid example as a demo instead

Fix Readonly plain text form alignment

Improvement to better understand how utilities class name are generated by the (_api.scss) base in the line of code below:
`$property-class: if($property-class, $property-class, nth($properties, 1));`

https://github.com/twbs/bootstrap/blob/fc02932946424e986a72bb7b47044eab815851cb/scss/mixins/_utilities.scss#L21

From #28948.

"Popovers whose both title..."

Fixed minor grammatical error:

"... the best method get scroll ..."

=>

"... the best method to get scroll ..."