Pages & Posts lists: Search border incorrect color when switching appearance

[ScoutHarris]

Expected behavior

When switching between light and dark modes, the border on the Search bar should be consistent.

Actual behavior

When switching light to dark, the Search bar border is white.
When switching dark to light the border is black.

Steps to reproduce the behavior

Go to either Site Pages or Blog Posts. Switch appearance. Notice the border color does not update.

Tested on [all], iOS [13.*], WPiOS [14.0]