PSA: removing quic, http2 and net from being collaborators subteam #35166

As discussed in #33984 and #34670, now that we have our own codeowners implementation, we should remove any team that is under collaborators as having teams under collaborators makes team management considerably harder.

I'll be removing the teams tomorrow. If you have any objections please share, but please also share ideas on how to keep things manageable.