Use ngrok v3 agents

[mpdude]

I have received a notification from ngrok:

We’re dropping you this end-of-year note because we’ve seen you connect to ngrok in the past 90 days with a soon-to-be-deprecated agent. We need to inform you that all ngrok agents version 3.1 and older will stop working on January 15th, 2024 for all free users.

This PR updates the download URLs to use the latest v3 agents.

I am always a bit sceptical when I see cryptic download URLs. In this case, you can cross-check the URL against the official ngrok documentation at the time of writing: https://github.com/ngrok/ngrok-docs/blob/1b7f012c469982a4ef389d1a85b63e6b21d904f5/docs/guides/device-gateway/linux.md

[luchihoratiu]

Hello and belated Happy New Year! 🎆

I just did a quick run with ubuntu-20.04, windows-2019 and macos-11.0. The URLs seem to be working as expected:

Thank you for being a debug-via-ssh user and, more importantly, for contributing to the project! 🌟

P.S. The very early heads up and proposed fix was really appreciated, but my response time couldn't reflect that sadly 😅