Added Group Descriptions to Exporters and updated Privacy Policy guide to drop use of deprecated classes

[garretthyder]

All Submissions:

• Have you followed the User Registration Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Adds support for group_description for privacy exporters which was added in WP5.3 through WPCoreChangeset#45825 and WPCoreTracTicket#45491

Update Suggested Privacy Policy text to utilize privacy-policy-tutorial css class instead of wp-policy-help as it was deprecated. Also wrap the contents in the wp-suggested-text div to style the section to match WordPress. This follows from WPCoreTrac#49282 and although back-compat is being introduced in WP5.4 as of WPChangeset#47112 this change will better support users of WP5.1-5.4

This also removes the wrapping

as it's now unnecessary. As long as the content uses the proper privacy-policy-tutorial class then the WP Privacy Policy Guide section copy action will avoid copying that content. The contenteditable divs were there originally when the contents was fully copied due to not using the appropriate class, and when originally the entire guide would be dumped into the WYSIWYG editor with wp-policy-help sections being highlighted.

How to test the changes in this Pull Request:

1. Install plugin and go to Privacy Policy Guide to view and test copy the contents.
2. Create a user with data and export to check the group description is added.

Types of changes:

• Bug fix (non-breaking change which fixes an issue)
• Enhancement (modification of the currently available functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully ran tests with your changes locally?
• Have you updated the documentation accordingly?

Changelog entry

• Added description to the privacy exporter group.
• Updated Privacy Policy Guide suggested content to use the correct css classes.