[fix] type definition update for typescript 4.8

[dominikg]

error:

/home/dominikg/develop/sveltejs/kit/.test-tmp/create-svelte/default-checkjs/src/lib/form.js:31:31
Error: A binding pattern parameter cannot be optional in an implementation signature. 
 */
export function enhance(form, { pending, error, result } = {}) {
        let current_token;

see microsoft/TypeScript#49869

first caught by vite-ecosystem-ci but also fails kit's own ci.

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