Remove unnecessary `assertLoggedIn` calls

In Sapper (the predecessor to SvelteKit), error handling wasn't terribly deterministic. So if in the [layout load function](https://kit.svelte.dev/docs/load#layout-data) e.g. `src/routes/members/+layout.server.ts` rejected the request with a not logged in error (HTTP 401), and the [page](https://kit.svelte.dev/docs/load#page-data) rejected the request with missing permissions (HTTP 403), it was pot luck as to which of the two errors got sent to the user. It seems like this is now resolved in SvelteKit, so we don't need to call `assertLoggedIn` in every handler for URLs starting with `/members`.