Expanding on how much better Proxy mode throughput is now

[tojens-ietf]

Summary

This updates the Windows, macOS, and linux release notes for our latest GA to make it clear just how much better proxy mode is. The original release already mentioned the improvement briefly.

Screenshots (optional)

N/A

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.