docs: add missing space in MCP params docstrings

[jluocsa]

Summary

The class docstrings for MCPServerSseParams and MCPServerStreamableHttpParams are missing a space before the backtick:

# before
"""Mirrors the params in`mcp.client.sse.sse_client`."""
"""Mirrors the params in`mcp.client.streamable_http.streamablehttp_client`."""

# after
"""Mirrors the params in `mcp.client.sse.sse_client`."""
"""Mirrors the params in `mcp.client.streamable_http.streamablehttp_client`."""

Without the space the inline code reference does not render as intended in generated docs. Two-line, docs-only change.

Checks

• ruff check src/agents/mcp/server.py — passes
• ruff format --check src/agents/mcp/server.py — already formatted