[commerce] Remove locale param from ShoppingServiceHandler constructor

We can now access the locale that the shopping service uses, there's
no need to access it through other means.

Bug: b:325501434
Change-Id: I9074f2ff9469e0120c3f1affc5f3fb338f018378
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5485261
Commit-Queue: Emily Shack <emshack@chromium.org>
Reviewed-by: Yue Zhang <yuezhanggg@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Reviewed-by: Emily Shack <emshack@chromium.org>
Auto-Submit: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1294994}