[Read Aloud] Add finch testing config for Read Aloud.

Bug: 340613875
Change-Id: If56b759c024a5c9505c2a5e5d2f47eea823eea7a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5539801


Reviewed-by: Kristi Saney <kristislee@google.com>
Commit-Queue: Lauren Winston <lwinston@google.com>
Cr-Commit-Position: refs/heads/main@{#1300857}