[LNA] cleanup more PNA references

Clean up some stale references to
PNA/private-network/private-network-access.

There are still a few references in
services/network/cors/preflight_controller.h/cc that might not be simple
deletions and will be cleaned up in a separate CL.

Bug: 394636065
Change-Id: Ic87883bc68402b50db3e9a7b9be68cf97fcff4c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7921548
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: mmenke <mmenke@chromium.org>
Commit-Queue: Hubert Chao <hchao@chromium.org>
Reviewed-by: Chris Thompson <cthomp@chromium.org>
Reviewed-by: Dominic Farolino <dom@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1648337}