remove unused import of get_mcp_auth_headers

Author: timof1308

src/google/adk/tools/mcp_tool/mcp_toolset.py

@@ -51,7 +51,6 @@
 from ._internal import sanitize_header_value
 from ._internal import validate_header_name
 from ._internal import validate_header_value
-from .mcp_auth_utils import get_mcp_auth_headers
 from .mcp_session_manager import MCPSessionManager
 from .mcp_session_manager import retry_on_errors
 from .mcp_session_manager import SseConnectionParams