Don't use links for headings in Ember Times

This is an issue that currently affects the production blog, so it could be done after the release :+1:

If you look at any of the Ember Times posts you will see that all of the headers are also links. This is not the best experience from an accessibility perspective and we need to change the structure of these headers

Right now the HTML is something like this:

```html

Using ember-concurrency with TypeScript 🤝

and we should really change it to something more like:

```html

Using ember-concurrency with TypeScript 🤝

Once we figure out how this should work in the Markdown then we should write some sort of script to update all of the posts that have this problem

Example:
- https://blog.emberjs.com/2020/07/17/the-ember-times-issue-156.html
- https://deploy-preview-7--ember-blog-legacy.netlify.app/the-ember-times-issue-156

Start by inspecting the Markdown and rendered HTML for the linked Ember Times issue 156 examples. Determine how the heading and external link should be represented in Markdown, then identify all affected posts for a migration. Done means headings are no longer links and separate external links render consistently across existing posts.

Written by the indexing model from the issue text.