This flag was used for IndexedDB support. Last uses in chrome were
removed in https://crrev.com/c/2013046, hence the API method can be
deprecated.

Also remove deserializer tests that were disabled by default or just
test that random bytes (from the deserializer's perspective) fail
to decode.

R=adamk@chromium.org

Bug: v8:10146
Change-Id: I8596849c3b51ab1c60272a49ff3fdaa0946452bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2013104
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65931}