Remove TLS13Experiment metrics

These expired a while ago and are a remnant of when we were monitoring
TLS 1.3 deployment issues.

Bug: 984283
Change-Id: I33f285fbb2ec7141c791847ef73de6feeedd1ea6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2844242
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Steven Valdez <svaldez@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#876926}
NOKEYCHECK=True
GitOrigin-RevId: 81655eb31d6ac647be040611a6ddcb44259de52e
3 files changed