Possible outdated YT reference in main README.md

[joshuax8]

Hi, just a quick check to confirm the following reference is left in place on purpose or not, following recent events:

MeshCore/README.md

Line 31 in 181a54e

- Watch the [MeshCore Intro Video](https://www.youtube.com/watch?v=t1qne8uJBAc) by Andy Kirby.

Thanks, keep up the good work!

[recrof]

see: #2567