fix: add missing sepolia env var to test.yaml [APE-717]

[antazoey]

What I did

Noticed failing build on main. Realized it needs the key. Nice, someone already added the key Oh, but what's this? The env var was forgotten in test.yaml no prob adds Now what? Does this count as a bug fix? Take that Vany. JK, too easy <3

How I did it

How to verify it

Checklist

• [ ] Passes all linting checks (pre-commit and CI jobs)
• [ ] New test cases have been added and are passing
• [ ] Documentation has been updated
• [ ] PR title follows Conventional Commit standard (will be automatically included in the changelog)

[antazoey]

Tests will fail because it is form fork, but should be ok to merge. The real test is if the build passes on merge to main.

[antazoey]

btw it worked!