5.0.1: row and cell background colours broken when using a non-transparent $table-bg (regression)

Created by: legoadk

Caused by fix for #33817 (closed).

If I have a $table-bg set via sass that's something other than transparent (for example, white), I can no longer change the cell background colour; it remains white.

Reversing the fix to #33817 (closed) resolves all of these issues.