Issue when RSS feed changes

[Choromanski]

I've noticed a few times that when the current rss feed updates to a new URL both the URLs end up in the database and end up getting synced to the application.

Example: https://feeds.megaphone.fm/armchair-expert-wide Now redirects to: https://rss.art19.com/armchair-expert

Both feeds exist in the DB now and are causing additional podcasts copies are being added to by application.

[bohwaz]

Can you provide a PR?