Remove or fix note about `dotenv-expand`

[tanberry]

Using this dotenv-expand only works if users have one of our .env files. The note needs to make this clear... or just remove the note.

See this thread: https://prisma-company.slack.com/archives/C016KUHB1R6/p1643669852467339

[janpio]

It might be that this note needs to be on a different page that is more about our .env files (if it does not exist there yet already).

[Jolg42]

Looks like a duplicate of https://github.com/prisma/docs/issues/2835 I didn't read the Slack thread mentioned here, but I made this PR https://github.com/prisma/docs/pull/4189