fix comment

Author: twishabansal

packages/toolbox-core/src/toolbox_core/sync_client.py

@@ -57,7 +57,7 @@ def __init__(
         async def create_client():
             return ToolboxClient(url)
 
-        # Ignoring type since we're already checking the existing of a loop above.
+        # Ignoring type since we're already checking the existence of a loop above.
         self.__async_client = asyncio.run_coroutine_threadsafe(
             create_client(), self.__class__.__loop  # type: ignore
         ).result()