Revert of [inspector] always include user scripts in the snapshot. (patchset #3 id:40001 of https://codereview.chromium.org/2836623002/ )

Reason for revert:
So that https://codereview.chromium.org/2841993002/ can be reverted.

Original issue's description:
> [inspector] always include user scripts in the snapshot.
>
> V8 can bundle user scripts in the start up snapshot. These are
> shared across contexts, and do not work well context groups.
>
> R=kozyatinskiy@chromium.org
> BUG=v8:6274
>
> Review-Url: https://codereview.chromium.org/2836623002
> Cr-Commit-Position: refs/heads/master@{#44847}
> Committed: https://chromium.googlesource.com/v8/v8/+/9685cfd310a51b2b32f97223069abaaca77405a8

TBR=kozyatinskiy@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:6274

Review-Url: https://codereview.chromium.org/2840923002
Cr-Commit-Position: refs/heads/master@{#44868}