The `double.json` corpus element is not in uppercase

[CLOVIS-AI]

The BSON corpus specification says:

canonical_bson: an (uppercase) big-endian hex representation of a BSON byte string. Be sure to mangle the case as appropriate in any roundtrip tests.

However, the double.json example contains examples where the canonical BSON representation isn't in uppercase:

• 1.2345678921232E+18 → 100000000164002a1bf5f41022b14300
• -1.2345678921232E+18 → 100000000164002a1bf5f41022b1c300