[Vaultwarden] Update "Update" Section

[remarcable]

When trying to update my vaultwarden instance I found that the steps in the Update section seemed to be incomplete.
I...

• Replaced the web-vault-feed link with https://github.com/dani-garcia/bw_web_builds/releases (it pointed to the vaultwarden repo)
• Add git checkout origin/async to apply new changes from remote after git pull

[pxlfrk]

Hi Marc, thanks for your contribution! :) Your Fix with the wrong link (web-feed) is correct.
But i'm not sure if adding another git checkout origin/async is necessary since or local branch should still be on that remote branch and git pull fetched the latest commits from that.

#1100 (comment)
Even since the async-branch hasn't got any updates in the last time it's still necessary to work in the uberspace environment. The official branch (main) depends on rust nightly which isn't available on uberspace - see further information in my linked comment in another issue. Hopefully this gets fixed soon and we can finally get rid of this clumpy workarround :)

[luto]

merged: 4477bd4

Thank you! :)