Restore tacocat expectation for null input value rerender

The previous flaky-fix commit changed `null: [ null, '' ]` while
splitting the double click. Preact 10.29.1 leaves `input.value` at
`'tacocat'` after the toggle pair (same observed behavior as the
`undef` row), so revert the matrix entry to match reality.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: cbravobernal

test/e2e/specs/interactivity/directive-bind.spec.ts

@@ -176,7 +176,7 @@ test.describe( 'data-wp-bind', () => {
 				values: {
 					false: [ null, 'false' ],
 					true: [ null, 'true' ],
-					null: [ null, '' ],
+					null: [ null, '', null, 'tacocat' ],
 					undef: [ null, '', null, 'tacocat' ],
 					emptyString: [ null, '' ],
 					anyString: [ null, 'any' ],