views: remove legacy preferred size from StyledLabel

This is a deprecated layout mode that is no longer in use. The only use
was removed in crbug.com/330641255.

Bug: 322715559
Change-Id: Iceaf3d050dae0ebeed3acb3f4db785a2606751e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5428390


Commit-Queue: Keren Zhu <kerenzhu@chromium.org>
Reviewed-by: Allen Bauer <kylixrd@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283631}