[Reader Mode] Readability Test Extension: Fix executeScript() order

On regular pages (but not the cloned page), the "Distill" and
"Distill New" features recently broke. This was caused by recent CL
crrev.com/c/7544257 , which alphabetized the order of the associated
scripts injected using chrome.scripting.executeScript().

This CL fixes the breakage by restoring the proper order, and adds
guarding comments.

Change-Id: I510d1a1df89c6a747688c1fe35518d86458e585b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7551571
Reviewed-by: Brandon Wylie <wylieb@google.com>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1581774}
NOKEYCHECK=True
GitOrigin-RevId: 295866dda98dceef738a5fa3dc97829a39900b7d