arrayify: Prefer `constexpr`

This CL is intended to be trivial. It marks the return from `std::to_array` as
`constexpr`. This CL is a split of a naive textual search-and-replace under:

content/browser/font_unique_name_lookup

This CL was uploaded by git cl split.

Change-Id: Ia7653568d29e5e7d7266af6d9052aedb3a5065ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6298212
Auto-Submit: Kalvin Lee <kdlee@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1424385}