Fix type of column_type parameter for handle_unknown_type method

The passed value of `column_type` parameter is not necessarily always
an `Object`. For example, `ActiveSupport::Types::Serialized` does not
have `Object` as an ancestor, since it is defined as:
```
class Serialized < DelegateClass(ActiveModel::Type::Value)
```
which makes it subclass from `BasicObject`.

We were using `Object` as the type for `column_type` parameter, but we
really wanted to use `BasicObject` instead.

I added a serialized column to a test case to see this fail before the
change and pass after the change.

lib/tapioca/dsl/helpers/active_record_column_type_helper.rb

@@ -75,7 +75,7 @@ def as_nilable_type(type)
           end
         end
 
-        sig { params(column_type: Object).returns(String) }
+        sig { params(column_type: BasicObject).returns(String) }
         def handle_unknown_type(column_type)
           return "T.untyped" unless ActiveModel::Type::Value === column_type
           return "T.untyped" if Runtime::GenericTypeRegistry.generic_type_instance?(column_type)