Remove @ts-expect-error on custom properties API once octokit types are updated

## Context

In `src/server/repos/controller.ts`, `octokit.rest.repos.getCustomPropertiesValues()` and `octokit.rest.orgs.getAllCustomProperties()` / `octokit.rest.orgs.createOrUpdateCustomProperty()` are currently suppressed with `@ts-expect-error` because `@octokit/plugin-rest-endpoint-methods` (bundled in octokit v5) does not yet include type definitions for these endpoints. (introduced in PR #484

The endpoints exist in the GitHub API and work correctly at runtime — the suppression is purely
a types gap.

## What needs to happen

Once the octokit upstream types are updated to include the custom properties endpoints, remove
the `@ts-expect-error` comments in `src/server/repos/controller.ts`.

## Upstream tracking

https://github.com/octokit/octokit.js/discussions/2050