The update where-builder flattened every AND eq predicate to a plain
value, which Prisma matches case-sensitively. On postgresql and mongodb,
incrementOne with a non-id insensitive guard found a mixed-case row with
findFirst but the keyed update missed it and returned null; update with
an id plus an insensitive filter did the same. Insensitive eq predicates
now stay in AND with mode, and plain eq keys stay flat for
WhereUniqueInput.