Upgrade Backup successful state design

[monsieur-z]

Changes proposed in this Pull Request

This PR updates the Backup successful screen to minimize the number of call-to-actions.

Fixes 1197351014149633-as-1197360555544603

Implementation notes

• I left post links in their original colour instead of black, for accessibility concerns

Testing instructions

• Download the PR
• Run Calypso with yarn start
• Run Jetpack cloud concurrently with yarn start-jetpack-cloud-p
• Pick a self-hosted Jetpack site that already has a backup
• Visit /backup/:site
• Check that you see the updates in both environments (see captures below)

Screenshots

Jetpack cloud

Before

After

Calypso

Before

After

[matticbot]

Test live: https://calypso.live/?branch=improve/backup-success-screen

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~109 bytes added 📈 [gzipped])

name      parsed_size           gzip_size
backup         +301 B  (+0.1%)      +71 B  (+0.1%)
activity       +127 B  (+0.0%)      +38 B  (+0.0%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[monsieur-z]

Automatic reformatting.

[elliottprogrammer]

Looks and works great!
LGTM! 👍

[monsieur-z]

I'm not sure if the failing check wait-calypso-live will break deployment. I'll deploy #46245 instead, which has the exact same diff and that passes all checks.