Stop multi-dimensional arrays from breaking

[dantownsend]

Related to piccolo-orm/piccolo_admin#369

If we have a table like this:

class MyTable(Table):
    my_column = Array(Array(Integer()))

It breaks FastAPIWrapper, because it tries to add a list[list] as a query param, which isn't allowed.

For now, lets change it to a body param, which is allowed.