Remove unnecessary send adapter (#878)

In previous versions of the `channels` library, the `send()` method
returned `bool` to indicate if the send was succesful or not. Recent
versions use exception to report errors and return `None`, making the
`send()` method directly compatible with what the resampler expects, so
we don't need an adapter any more.

Author: llucax

src/frequenz/sdk/actor/_resampling.py

@@ -87,10 +87,7 @@ async def _subscribe(self, request: ComponentMetricRequest) -> None:
             Sample[Quantity], request_channel_name
         ).new_sender()
 
-        async def sink_adapter(sample: Sample[Quantity]) -> None:
-            await sender.send(sample)
-
-        self._resampler.add_timeseries(request_channel_name, receiver, sink_adapter)
+        self._resampler.add_timeseries(request_channel_name, receiver, sender.send)
 
     async def _process_resampling_requests(self) -> None:
         """Process resampling data requests."""