Remove telomere reporting client logic and buildflags

Removes TelomereEventRouter, TelomereReportingContext, and associated
ENTERPRISE_TELOMERE_REPORTING buildflags and preference constants.
This event was an unlaunched prototype that is being retired.

This is Phase 2 (Chromium CL 1) of the cleanup of unlaunched
experiments DoNotLaunchEnablePrototypeRawEvent and EnableTelomereEvent.

Bug: 509617293, 509616298
Change-Id: I986026daf35690aabf06926dad5e4c50af2e5393
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8501941
Commit-Queue: Shanthanu Bhardwaj <xanth@google.com>
Reviewed-by: Dominique Fauteux-Chapleau <domfc@chromium.org>
Reviewed-by: Monica Salama <msalama@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1710266}