fix(test): remove unsupported SSE Bruno cases (#2800)

Why this change was needed:
The SSE initialize Bruno cases opened long-lived SSE GET connections as normal HTTP requests. Bruno CLI waits for the response body to finish, but MCP SSE endpoints intentionally keep the connection open after sending the endpoint event, causing maxContentLength failures during e2e runs.

What changed:
- Removed the app-mode SSE initialize Bruno case
- Removed the user-mode SSE initialize Bruno case
- Kept Streamable HTTP MCP cases as the Bruno-covered path

Problem solved:
The Bruno e2e suite no longer fails on unsupported long-running SSE connection cases. Full SSE protocol coverage remains better suited for SDK-based integration tests.

Co-authored-by: claude <noreply@anthropic.com>

Author: Han-Ya-Jun