Character count size changes when error state is applied

[36degrees]

The size of the character count changes when you go over the character limit.

This is happening because we're still trying to compensate for the error state having a thicker border, which it no longer does since #1870.

govuk-frontend/src/govuk/components/character-count/_index.scss

Lines 15 to 17 in 7f6a45e

	.govuk-textarea--error {
	padding: govuk-spacing(1) - 2; // Stop a "jump" when width of border changes
	}