RNv2: Channel unarchived websocket event does not add the channel back into the channel list

Right now, we are only setting the channel delete at to 0.

If the channel has been deleted from the local database, we do not fetch it again, so it will only be visible if we reload the app.

Steps to reproduce:

• Make sure that Allow users to view archived channels is set to false
• Open the app and have the list of channels with channel A visible
• In a different client, archive channel A
• (Expected) Channel A disappears from your list of channels in the app
• Without doing anything else in the app, in a different client, go to the System console and unarchive that channel.

Expected:

• The channel reappears in the channel list

Observed:

• The channel does not appear in the channel list until we restart the app

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JIRA: https://mattermost.atlassian.net/browse/MM-49201