fix: correct route variable names from *_url to *_path

Signed-off-by: Shingo OKAWA <[email protected]>

Author: ognis1205

src/a2a/server/apps/starlette_app.py

@@ -683,13 +683,13 @@ def routes(
         """
         return [
             Route(
-                rpc_url,
+                rpc_path,
                 self._handle_requests,
                 methods=['POST'],
                 name='a2a_handler',
             ),
             Route(
-                agent_card_url,
+                agent_card_path,
                 self._handle_get_agent_card,
                 methods=['GET'],
                 name='agent_card',