Authorize flow links to a page explaining Jetpack Sync, it's not always needed

See https://github.com/Automattic/wp-calypso/pull/41798#issuecomment-642734235 for more context.

I wasn't sure where to open this issue, mainly because I don't know exactly what the approach should be.

In the Jetpack authorize screen in Calypso, there's this blurb of text:

> By connecting your site, you agree to [share details] between WordPress.com and YOUR_BLOG_NAME.

`share details` is a link to https://jetpack.com/support/what-data-does-jetpack-sync/

The wording of that blurb makes me think it's there for legal purposes.

However, it may not be always needed. If a plugin is using just `jetpack-connection` without also using `jetpack-sync`, then there won't be any data shared between WP.com and the site at all, so that disclaimer is not needed. For privacy-conscious users, that may play a big factor when onboarding into, say, a payment gateway.

However, if later the user install Jetpack-the-plugin or any other plugin that includes `jetpack-sync`, should the user authorize again, for legal purposes?

I think a possible solution would be for the `sync` package to filter the `jetpack_connect_request_body` payload to add a parameter like `sync_enabled=true`, or similar, and then Calypso should only show the disclaimer if `sync_enabled` is set. Or something similar. What do y'all think?

Props to @vbelolapotkov for realizing the link was there in the first place :)

Start at the Jetpack authorize screen in Calypso and trace the jetpack_connect_request_body payload and the sync package mentioned in the issue. Determine whether the disclaimer should depend on sync_enabled, then confirm the authorization and later-plugin-install behavior before defining tests and completion criteria.

Written by the indexing model from the issue text.