Offer a button to retry checking for updates

Problem Description

I'm not precisely sure what I did, but it's possible my laptop moved between networks/was on a broken network...

Rancher Desktop 1.15.0 showed me:

There was no obvious way to get it to check again. (Exiting and restarting did eventually get me an update prompt, which did let me get 1.15.1 in time to be told by @jandubois that there's a 1.16.0, but that's another story.)

Proposed Solution

Add a button to check for updates to the failed flow

Additional Information

#1929 talks about cases where some update check fails.