Fix v6 tag and remove obsolete v7 tag

Adds missing ajs into the v6 tag. The v6 tag correctly includes this when generated from [portal](https://github.com/mobify/portal_app/blob/master/portal/templates/core/tag_6.html).
  
Also removed the obsolete version of the v7 tag that never ended up being developed. @jansepar wrote a new version instead.

Status: **Opened for visibility**
 
Reviewers: @jansepar @noahadams @tedtate 
  
## Changes
- Remove v7 tag bootstrapper
  
## How to test-drive this PR
- Host the tag locally, and inject it into a project. Confirm that ajs loads correctly when the unmobified experience is loaded. Also ensure the normal tag flow doesn't break.