This reverts commit f388f96f.

Reason for revert: Crashes in canary (https://crbug.com/1360024)

Original change's description:
> Enable background merging of deserialized scripts
>
> This can save memory in cases where multiple frames in a process use the
> same script, with sufficient time between loads that the script's
> top-level SharedFunctionInfo is no longer present in the compilation
> cache. Merging is relatively fast; it generally takes about one tenth as
> long as deserialization.
>
> Bug: v8:12808
> Change-Id: I7366a51f1d2ca6a9f551cdf2bdbe0441450cf1bb
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3868088
> Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#82920}

Bug: v8:12808
Change-Id: If160173afaab351d995ddcf4b60d6efe656cf70b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3871208
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#82983}