streams: Allow editing subscriptions in archived channels.

Since this does impact the ability to access the channel's content, it
makes sense to permit changing subscriptions, just like other
permissions settings on the archived channel.

zerver/lib/streams.py

@@ -500,7 +500,7 @@ def access_stream_for_send_message(
         else:
             raise JsonableError(_("User not authorized for this query"))
 
-    # Deactivated streams are not accessible.
+    # You cannot send mesasges to archived channels
     if stream.deactivated:
         if archived_channel_notice:
             return
@@ -1262,9 +1262,7 @@ def filter_stream_authorization_for_adding_subscribers(
         )
 
     unauthorized_streams = [
-        stream
-        for stream in streams
-        if stream.deactivated or stream.id not in content_access_stream_ids
+        stream for stream in streams if stream.id not in content_access_stream_ids
     ]
     unauthorized_stream_ids = {stream.id for stream in unauthorized_streams}