fix(postgres): Fix exp.WidthBucket required args

[VaggelisD]

Fixes #6620

Postgres supports the following variants:

width_bucket ( operand numeric, low numeric, high numeric, count integer ) → integer

width_bucket ( operand double precision, low double precision, high double precision, count integer ) → integer

width_bucket ( operand anycompatible, thresholds anycompatiblearray ) → integer

It is probably better to create a new arg to capture the array but didn't bother with it

Docs

Postgres functions