Revert "isolate: introduce instrument_endpoint to WebUI"
Revert "isolate: introduce instrument_endpoint to WebUI"

This reverts commit 1a944d7eaab90ea3f6d11c00d2b157b7d1ca57da.

Reason for revert:
Stats for /browse, /content handler were already there.
https://screenshot.googleplex.com/G9O43uKaXpQ

Original CL added stats with name /_ah/spi/BrowseHandler.get,
but that is duplication.
https://screenshot.googleplex.com/bSd0veB6eSV

Original change's description:
> isolate: introduce instrument_endpoint to WebUI
>
> Before considering CAS viewer, let me take stats how often the endpoint
> is accessed.
>
> Bug: 924661
> Change-Id: Ifa8bcbbe26ebae6f107dd7764734288c4da2000f
> Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2067003
> Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
> Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
> Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>


# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 924661
Change-Id: Id16717e74734a1876ac92144bc03ba9e0e8889f0
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2124189
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py