[v9] Go through `TODO(v9)` comments in docs

### Description

For v9 compatible docs we added documentation that should be removed when v9 ships. These have been annotated with `TODO(v9)` comments. Example: https://github.com/getsentry/sentry-docs/blob/fdf7a7a52cf0edb9592d5671a7514407fdb6183e/platform-includes/getting-started-use/javascript.nestjs.mdx#L52-L53

We should remove all of these docs.