streams: Deleting a stream doesn't update browser properly.

[rishig]

It seems like deleting a stream:

• Changes the stream color to gray
• Removes the stream messages from All messages

Neither of those happen until you reload Zulip, though.
You do see the gray behavior if you search for the stream's messages via search, but not if you go to All messages.

[zulipbot]

Hello @zulip/server-message-view members, this issue was labeled with the "area: message view" label, so you may want to check it out!

[kasthuri28]

@rishig I would like to know, as a beginner in contributing to open source will it be good for me to start my contribution with this issue. If yes please guide me how to begin with.