remove old intro pricing news entry

[groovecoder]

This PR removes the intro pricing news entry: the only part of the code that dependended on fast-check, so we don't have to keep up with its updates.

How to test:

1. cd frontend && npm run watch
2. python manage.py collectstatic
3. python manage.py runserver
4. Sign in to http://127.0.0.1:8000/accounts/profile/
5. Click "News" in the top navigation
6. Click the "History" pill button
   • You should NOT see the news item about introductory pricing (note: a waffle flag might already be hiding it)
   • The rest of the News items should all still work

• l10n changes have been submitted to the l10n repository, if any.
• I've added a unit test to test for potential regressions of this bug.
• I've added or updated relevant docs in the docs/ directory.
• All UI revisions follow the coding standards, and use Protocol tokens where applicable (see /frontend/src/styles/tokens.scss).
• Commits in this PR are minimal and have descriptive commit messages.

[rafeerahman]

thanks, the I don't see the introductory pricing news item anymore.