doc: remove teredo/miredo, linnk to awesome-tunneling

all public teredo services are discontinued?

• remlab offline as of Jun 2021
• https://www.trex.fi/service/teredo.html offline as of 2022

It's possible for someone to host their own, but then they'd have access to a public IP.

Awesome tunneling links to alternatives.

added 3 commits

• 3b93786f...a25188da - 2 commits from branch qhong:master
• cc1e1da4 - Merge branch 'master' into 'no_miredo'

Compare with previous version

mentioned in commit d9ea57d4

merged