Decommission old VPN landing page template (Fixes #15226)

[alexgibson]

One-line summary

Removes old VPN landing page and pricing page templates.

Issue / Bugzilla link

15226

Testing

• http://localhost:8000/en-US/products/vpn/
• http://localhost:8000/en-US/products/vpn/pricing/

Things to verify:

• Check I didn't remove any shared strings that are still in use.
• Check i didn't remove any images that are still in use.
• Check I didn't remove any SCSS/JS files that are still in use.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.42%. Comparing base (2a7caf9) to head (1d8694b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15243   +/-   ##
=======================================
  Coverage   78.41%   78.42%           
=======================================
  Files         162      162           
  Lines        8350     8344    -6     
=======================================
- Hits         6548     6544    -4     
+ Misses       1802     1800    -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[alexgibson]

Successful test run: https://github.com/mozilla/bedrock/actions/runs/11162618506

[craigcook]

Looks good, but some suggestions for additional tidying if you're up for it. If you'd rather do those things separately this is good to merge (though should still remove the HELLO to play it safe). r+wc 🥔