refactor: Split proposal - keep Events API only in this PR

The Table Metrics REST API proposal has been moved to a separate PR apache#4010
to allow independent progress on both proposals.

This PR now contains only the Events REST API proposal.

Requested by: @dimas-b in review comment

Author: Anand Kumar Sankaran

site/content/in-dev/unreleased/proposals/_index.md

@@ -31,5 +31,4 @@ This section contains design proposals for new features and enhancements to Apac
 | Proposal | Status | Description |
 |----------|--------|-------------|
 | [Events REST API](events-rest-api.md) | Draft | REST API endpoint for querying catalog events (Iceberg Events API compatible) |
-| [Table Metrics REST API](table-metrics-rest-api.md) | Draft | REST API endpoints for querying table scan and commit metrics |