new mypy version fixes weird type issue

Author: rmorshea

requirements/extras.txt

@@ -1,5 +1,5 @@
 # extra=sanic
-sanic >=19.9.0, <20.0
+sanic >=19.12.0, <20.0
 sanic-cors >=0.9.9, <1.0
 
 # extra=matplotlib

src/py/idom/core/render.py

@@ -87,11 +87,7 @@ def __init__(self, layout: AbstractLayout) -> None:
     async def run(self, send: SendCoroutine, recv: RecvCoroutine, context: str) -> None:
         self._updates[context] = asyncio.Queue()
         try:
-            await asyncio.gather(
-                super().run(send, recv, context),
-                # not sure why `Future[None]` isn't allowed here
-                self._render_task,  # type: ignore
-            )
+            await asyncio.gather(super().run(send, recv, context), self._render_task)
         except Exception:
             del self._updates[context]
             raise