fix(types): use MutableMapping to type call arguments in asgi middleware

When we bumped `opentelemetry-instrumentation-asgi` to 0.45b0, we got type errors due to the changes introduced by PR open-telemetry#2026.

```
error: Argument 1 to "add_middleware" of "Starlette" has incompatible type "type[AsgiMiddleware]"; expected "type[_MiddlewareClass[[]]]"  [arg-type]
```

The problem is that it is specifying the types as `dict`, whereas Starlette requires `MutableMapping`. See https://github.com/encode/starlette/blob/9f16bf5c25e126200701f6e04330864f4a91a898/starlette/types.py#L10-L14.

I first tried to change the type to `MutableMapping`, but that produces lot of extra changes as the code is not fully typed and we seem to be using `dict`s everywhere.

instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py

@@ -553,12 +553,7 @@ def __init__(
             or []
         )
 
-    async def __call__(
-        self,
-        scope: dict[str, Any],
-        receive: Callable[[], Awaitable[dict[str, Any]]],
-        send: Callable[[dict[str, Any]], Awaitable[None]],
-    ) -> None:
+    async def __call__(self, scope, receive, send) -> None:
         """The ASGI application
 
         Args: