#2900696 Update the reconnect to renew message on the Manage Purchase page

This PR updates the message on the Manage Purchase page for expired and disconnected sites. Instead of recommending contacting the support, it now informs that the site has to be reconnected to WordPress.com in order to be renewed.

This should resolve the issue described in pbtFFM-5K-p2

Changes proposed in this Pull Request

• Update the footer message copy for expired and disconnected sites
• Use a more semantic and content-agnostic class name for the message container

Testing instructions

• Set up a Jetpack site (e.g. Jurassic Ninja) with one of the paid plans
• In SA, manually adjust the “expires” date, so that the plan is expired
• Disconnect the site from WordPress.com
• Go to http://calypso.localhost:3000/me/purchases and select the site with the expired plan
• Confirm that the message on the https://wordpress.com/me/purchases/:siteSlug/:purchaseId is now updated and clearly communicates the next step

Fixes n/a