Remove wrapper API around custom user education event.

User education events didn't used to be exported. This means that we
needed to use an exported wrapper API in order to watch for a custom
user education event from production in test code for component builds.

As of recently, custom user education events are now exported and so
the wrapper API is no longer necessary:

https://crrev.com/c/chromium/src/+/4834696

Bug: b:287129131
Change-Id: I1235ef24d5bd5931a5991961d0b46c18d9e73924
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4892465
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/main@{#1201879}