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:

chrome/browser/history

This CL was uploaded by git cl split.

Change-Id: If063cdc8db49be6764d66cc77777d2315a48c4fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6301468
Auto-Submit: Kalvin Lee <kdlee@chromium.org>
Reviewed-by: Sophie Chang <sophiechang@chromium.org>
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1424644}