fix SP1_DEV for nightly CI

[huitseeker]

After #40, we don't run the plonk e2e test ( test_e2e_prove_plonk) in CI, except in nightlies, and there the test is unlikely to succeed unless we set SP1_DEV=true, in ways @storojs72 detailed in his messages elsewhere.

We do set FRI_QUERIES, but not SP1_DEV:
https://github.com/lurk-lab/sphinx/blob/785d0e01c92133152fe534bb181f2f80ef180d78/.github/actions/setup/action.yml#L23