Replaces a custom hsla() value (dunno what I was thinking when I added this) with a reassigned existing variable. This variable goes up the stack and attaches to the $component-active-bg variable, derived from our $primary color out of the box.
The variable of choice was $input-focus-border-color, which is applied to the border of our switches anyway, so now the inside of the switch matches the border. This is a slightly darker color, too, which is an improvement IMO.
Fixes #30646 (closed).