event stream: set timeout to 20 seconds for reading

This will hopefully catch if we aren't getting any heartbeats or
com.linkedin.realtimefrontend.ClientConnection events.

Signed-off-by: Sumner Evans <[email protected]>

linkedin_messaging/linkedin.py

@@ -559,7 +559,7 @@ async def _listen_to_event_stream(self):
                 raise TooManyRequestsError(f"Failed to connect. Status {resp.status}.")
 
             while True:
-                line = await resp.content.readline()
+                line = await asyncio.wait_for(resp.content.readline(), timeout=20)
                 if resp.content.at_eof():
                     break