fix: override turbo_api env var (#7234)
### Description
For some reason Hetzner is setting `TURBO_API` which is causing us to
not use the remote cache
[e.g.](https://github.com/vercel/turbo/actions/runs/7757236744/job/21156328810?pr=7223#step:6:79)
### Testing Instructions
Verify that JS Packages now uses the correct remote cache (no remote
cache warnings):
[job](https://github.com/vercel/turbo/actions/runs/7759230611/job/21162847801?pr=7234#step:6:1)
Closes TURBO-2226
