fix: Make MuxRPCAPI.__await__ a sync method

ssb/muxrpc.py

@@ -134,16 +134,23 @@ class MuxRPCAPI:
         self.handlers = {}
         self.connection = None
 
-    async def __await__(self):
-        async for req_message in self.connection:
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        req_message = await self.connection.__anext__()
+
         if req_message is None:
-                return
+            raise StopAsyncIteration()
 
         body = req_message.body
 
         if isinstance(body, dict) and body.get("name"):
             self.process(self.connection, MuxRPCRequest.from_message(req_message))
 
+    def __await__(self):
+        yield from self.__anext__().__await__()
+
     def add_connection(self, connection):
         """Set the packet stream connection of this RPC API"""