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

[Miablo]

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

octokit/octokit.js#2050