Corrected `since_id`/`until_id` types on v2 Events SSE endpoints

Broker API

Corrects the documented query parameters on the v2 Events SSE endpoints:

• since_id and until_id are now documented as ULID strings rather than integers.
• Removes references to the non-existent since_ulid and until_ulid parameters.

Affected Endpoints

• GET /v2/events/funding/status
• GET /v2/events/journals/status
• GET /v2/events/system