chore: remove unused env vars from Cross.toml (#4717)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

Followup to #4703 and #4705.

## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [ ] I have tested the changes locally.
- [ ] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

.github/Cross.toml

@@ -2,8 +2,6 @@
 passthrough = [
     "HOME",
     "RUST_BACKTRACE",
-    "BARRETENBERG_BIN_DIR",
-    "BLNS_JSON_PATH"
 ]
 volumes = [
     "HOME",