Close receiver when stopping LatestValueCache

Signed-off-by: Sahas Subramanian <sahas.subramanian@proton.me>

Author: shsms

src/frequenz/channels/_latest_value_cache.py

@@ -53,6 +53,9 @@ class LatestValueCache(typing.Generic[T_co]):
 
     It provides a way to look up the latest value in a stream without any delay,
     as long as there has been one value received.
+
+    Takes ownership of the receiver.  When the cache is stopped, the receiver
+    will be closed.
     """
 
     def __init__(
@@ -109,6 +112,7 @@ async def _run(self) -> None:
 
     async def stop(self) -> None:
         """Stop the cache."""
+        self._receiver.close()
         if not self._task.done():
             self._task.cancel()
             try: