shortcuts: Fix scroll to accelerator repeating incorrectly

Before, when you selected a search result that existed in the current
category, and then navigate away from that category and back again,
the app would scroll to that accelerator again instead of resetting to
the top of the page.

This CL fixes that bug by resetting the route after the scroll event,
as we already do when scrolling to a new page.

Before:
http://go/scrcast/NTk1MTAzODA2MzM3ODQzMnwwZjQ0YzlhOS0wNw

After:
http://go/scrcast/NDY2NTQ2ODQ1MjMzOTcxMnw3ZTY1ZTlmOC0yOQ

Change-Id: Iab3517ac40f8eb3c1f946ccf1c84b888b132d082
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4549720


Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Commit-Queue: Camden Bickel <cambickel@google.com>
Cr-Commit-Position: refs/heads/main@{#1146747}