follow-up to
- https://github.com/nushell/nushell/pull/10715
> **Important**
> wait for between 0.87 and 0.88 to land this
# Description
it's time for removal again 😋
this PR removes `def-env` and `export def-env` in favor of `def --env`
# User-Facing Changes
`def-env` and `export def-env` will not be found anymore.
# Tests + Formatting
# After Submitting