language_packs: Enable handwriting base payload by default

This change will make Language Packs the default logic for handwriting
starting M119.

I've removing the relative fieldtrial testing config entry as well, as
required by the Finch guidelines.

Bug: b:280933640
Change-Id: I9f920dd3f5b1879a60befe509ef3be6a6311137b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4904452
Commit-Queue: Claudio M <claudiomagni@chromium.org>
Reviewed-by: John Palmer <jopalmer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1204484}