[views-ax] Cleanup of GetTooltipText (part 1)

This is the first cleanup in the refactor of caching tooltip text on
views. This one involves removing overrides that just returned the
cached value, which is already returned by the base version of
`GetTooltipText(point)`

This CL is part of the ViewsAX project:
https://docs.google.com/document/d/1Ku7HOyDsiZem1yaV6ccZ-tz3lO2XR2NEcm8HjR6d-VY/edit#heading=h.ke1u3utej413

Bug: 325137417
Change-Id: I0ba52fdd568b763369d5b7ccae8c2ca7d02e5e84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6089515
Reviewed-by: Elly FJ <ellyjones@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Javier Contreras <javiercon@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1395477}