[BUG]: .default() method accepts Date object but should only accept SQL

### What version of `drizzle-orm` are you using?

0.29.1

### What version of `drizzle-kit` are you using?

0.20.6

### Describe the Bug

This relates to https://github.com/drizzle-team/drizzle-orm/issues/1105#issuecomment-1879238290.

When using an integer column in timestamp mode, the `.default` method accepts a type of `SQL | Date`. It should only accept `SQL`.

A consequence of this is that developers who try to generate migrations using a `Date` object will end up with a script that does not execute.

See screenshot of function argument type annotation:

### Expected behavior

The function argument type should only be `SQL`

### Environment & setup

Tested on NodeJS 20