Add explanation for soft deletion to user delete function (#838)

## What kind of change does this PR introduce?

docs update to provide explanation of soft deletion for delete user
endpoint

## What is the current behavior?

closes supabase/supabase#20057

## What is the new behavior?

Explains what the soft delete flag does so it can be picked up in the
Supabase docs

## Additional context

Add any other context or screenshots.

src/GoTrueAdminApi.ts

@@ -260,7 +260,7 @@ export default class GoTrueAdminApi {
    * Delete a user. Requires a `service_role` key.
    *
    * @param id The user id you want to remove.
-   * @param shouldSoftDelete If true, then the user will be soft-deleted from the auth schema.
+   * @param shouldSoftDelete If true, then the user will be soft-deleted (setting `deleted_at` to the current timestamp and disabling their account while preserving their data) from the auth schema.
    * Defaults to false for backward compatibility.
    *
    * This function should only be called on a server. Never expose your `service_role` key in the browser.