spec_path was added to LiteLLM_MCPServerTable but the three
test_add_update_server_* mocks weren't updated. MagicMock auto-creates
a MagicMock for unset attributes, which fails the Optional[str] Pydantic
validation. Fixes test_add_update_server_with_alias,
test_add_update_server_without_alias and
test_add_update_server_fallback_to_server_id.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>