Delete GetWifiPHYLayerProtocol().

This API was only implemented on Windows and used from two places:
  - For UMA reporting
  - For the description of the connection object

I believe both of these may not be needed.
This API call results in a permission prompt on newer versions of
Windows, which is not desirable.

Bug: 345798486
Change-Id: I32be861fd204a826af445b11cdd88a59ff0b8766
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5615430


Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312901}