Remove normalize-fixes.css

Problem/Motivation

In #3123832: [META] Fix @todo items referencing closed issues we discovered that there's a @todo in
core/themes/stable9/css/core/normalize-fixes.css which references a d.o. issue that is already closed; #3114878: The webkit search cancel button should not be hidden

Here's the @todo:

/**
 * Prevent regression due to normalize.css no longer hiding the cancel search
 * button in 8.0.0.
 * @todo Remove this rule in https://drupal.org/node/3114878
 */
input[type="search"]::-webkit-search-cancel-button {
  -webkit-appearance: none;
}

Proposed resolution

So #3114878: The webkit search cancel button should not be hidden was closed as a duplicate of #3309317: Remove normalize-fixes.css.

In that issue, we removed core/misc/normalize-fixes.css.
That file was 100% identical to core/themes/stable9/css/core/normalize-fixes.css.

So for the same reasoning that was made in #3309317: Remove normalize-fixes.css:

Remove the entire file. We no longer support IE or non-Chromium versions of Edge. #3114878: The webkit search cancel button should not be hidden already proposes removing the Webkit fix.

I think we can remove this in Stable9 as well.

If, for backwards-compatibility, we can't delete it, we should delete the @todo

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet