Revert "Add UMA logging of implemented WebView callbacks"

This reverts commit 8251daa6.

Reason for revert: Reflection causes NonSdkApiUsedViolation
                   b/339432838

Original change's description:
> Add UMA logging of implemented WebView callbacks
>
> Bug: 339432838
> Change-Id: I1a28801ca612a3f7f14bdb7cf91de5239430f6c6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5526660


> Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
> Reviewed-by: Peter Conn <peconn@chromium.org>
> Commit-Queue: Peter Pakkenberg <pbirk@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1298598}

Bug: 339432838
Change-Id: I0d3484e0d1cd223329c86dbb68f9f04e4937d745
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5611342


Commit-Queue: Peter Pakkenberg <pbirk@chromium.org>
Reviewed-by: Peter Conn <peconn@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312679}