Add Flathub link to VPN download page

[wen-2018]

If this changeset needs to go into the FXC codebase, please add the WMO and FXC label.

One-line summary

This PR adds flathub link to VPN download page. Figma design

Significant changes and points to review

Flathub link in primary and secondary cards.

Issue / Bugzilla link

#16552

Testing

http://localhost:8000/en-US/products/vpn/download/ (using Linux to test primary card and non-linux system to test secondary card)

┆Issue is synchronized with this Jira Task
┆Priority: P2
┆Sprint: Backlog

[maureenlholland]

r+wc
Minor blocker on missing SVG viewbox

Local integration tests all passed ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.68%. Comparing base (20449c1) to head (d5814aa).
⚠️ Report is 33 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16782      +/-   ##
==========================================
- Coverage   79.68%   79.68%   -0.01%     
==========================================
  Files         159      159              
  Lines        8522     8525       +3     
==========================================
+ Hits         6791     6793       +2     
- Misses       1731     1732       +1     

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[maureenlholland]

r+ 💯