IDB: delete some low value tests.

These tests are very tightly coupled to implementation details specific
to LevelDB. The coverage they provide is extremely limited as they only
verify a single very specific behavior, i.e. how the system deals with
schema or data encoding versions that are less than zero, but don't
verify behavior of any other unexpected value.

Ultimately it's not even very important how IDB behaves in these
situations, in that if the production code that returns errors when
these values are under 0 were removed for some reason, the failure
modes would still be entirely reasonable:

. For very low schema versions (from before 2014), IDB will already
throw an error, so additionally verifying >= 0 doesn't catch any more
bugs.

. The only reason to track data encoding versions is to catch databases
that used encodings which are too *new*, i.e. a newer version of
Chromium created this file. Checking for values less than 0 doesn't
accomplish that. This number doesn't actually describe the encoding
scheme used for the SerializedScriptValues in the database, as those are
encoded in each serialized byte stream. Rather this number describes the
newest version of data serialization that *might* be found in the
database. If the actual serialized data is corrupted that would be
handled in due course when trying to deserialize the data.

Since the tests provide so little value, they are not ported to a SQLite
world or to unit tests, but rather deleted.

Bug: 40273263
Change-Id: I1733a92cbac1f0b024d6a945a5993c0b8fad54b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6460622
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Abhishek Shanthkumar <abhishek.shanthkumar@microsoft.com>
Commit-Queue: Evan Stade <evanstade@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1447792}