fixup! Improve the _sender module description

Author: llucax

src/frequenz/channels/_sender.py

@@ -19,9 +19,9 @@
 await sender.send("Hello, world!")
 ```
 
-Even when [`send()`][frequenz.channels.Sender.send] is an asynchronous method, some
-channels may implement it as a synchronously. For example, buffered channels that
-drop messages when the buffer is full could guarantee that
+Although [`send()`][frequenz.channels.Sender.send] is an asynchronous method, some
+channels may implement it in a synchronous, non-blocking way. For example, buffered
+channels that drop messages when the buffer is full could guarantee that
 [`send()`][frequenz.channels.Sender.send] never blocks. However, please keep in mind
 that the [asyncio][] event loop could give control to another task at any time,
 effectively making the [`send()`][frequenz.channels.Sender.send] method blocking.
@@ -58,7 +58,7 @@
 
 
 class Sender(ABC, Generic[_T]):
-    """An entity that sends values to a *channel*."""
+    """An endpoint to sends messages."""
 
     @abstractmethod
     async def send(self, msg: _T) -> None: