Prefer `array?` rather than `array`

Happy New Year! :tada: :sheep:

`array` can only be called to check to dump the `:array` option in the AR internal, therefore it is not necessary to determine until it is called. Do not remove `[]` from `sql_type` for the `array?` method. Lookup the `cast_type` from `sql_type` required `[]` also. It was not necessary to remove `[]`.
I think, now we are setting incorrect  `sql_type` value in case of array.

```
# Earlier
@sql_type  = sql_type[0..sql_type.length - 3]

# Now
@sql_type  = sql_type
```