dotfiles: drop the non-elevated ETW tracing, it never worked

dotfiles: drop the non-elevated ETW tracing, it never worked

Putting an ordinary account into Performance Log Users was supposed to
buy user-mode ETW collection without a UAC prompt. Testing the actual
workflow says otherwise: xperf and VTune want an administrator account
and an elevated prompt, and everything short of that gets blocked
somewhere. The kernel logger was already known to be admin-only; the
rest turned out not to be worth the machinery either.

So the -TraceUser and -EtwRightsOnly parameters, the group membership
step, and the UAC launch line that existed only to carry an argument
across the elevation boundary all come out. The launch line goes back to
the single-argument form it had before.

Kept, because they are useful whether or not collection is elevated: the
Windows Performance Toolkit step that detects xperf/wpr/wpa, reports
their versions and puts them on the machine PATH, and the VTune step
that reports whether it is installed.

The README keeps the negative result rather than quietly losing it, and
gains the commands to undo what earlier revisions left on a box - the
group membership, the privilege, and the ACE.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012gCzbrN6p3emFUyufuJsyq