[DOCS]: Recommend using `generatedAwaysAsIdentity` in PG instead of `serial` data type

### Report hasn't been filed before.

- [X] I have verified that the bug I'm about to report hasn't been filed before.

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

0.36.1

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

0.28.0

### Other packages

_No response_

### Describe the Bug

I am reporting this bug in the hopes that the docs will be updated as it results in countless issues.

The Postgres docs still mention using `serial()` as a datatype but this has been deprecated it will throw errors across different stages.

For anyone reading this: do not using `serial` with Postgres.