Off-canvas styling for autocomplete search results make them difficult to read

Autocomplete search results in an off-canvas form (like a custom block in layout builder) are nearly impossible to read:

Steps to reproduce:

1. Install site on 8.6.x or 8.7.x with standard install profile
2. Enable layout builder module
3. Add several terms to the existing "Tags" vocabulary
4. Add a custom block type with a term reference field to the tags vocab
5. Enable layout builder for the existing "Basic Page" content type
6. Edit layout, and add your custom block to the page
7. Search for terms in the autocomplete field, and observe that the results list displays dark gray text on a slightly darker gray background

The reason it happens is a combination of these two rules:

off-canvas.base.css has this:

#drupal-off-canvas *, #drupal-off-canvas *:not(div) {
    background: #444;
    font-family: "Lucida Grande", "Lucida Sans Unicode", "liberation sans", sans-serif;
    color: #ddd;
}

That sets the background of the autocomplete <li> to that dark color.

Then we have this in off-canvas.form.css:

#drupal-off-canvas .ui-autocomplete li a {
    color: #595959 !important;
    cursor: pointer;
    padding: 5px;
}

Which sets the links to that dark gray.