Style-based benchmarks are broken

[mourner]

Style-based benchmarks (such as http://localhost:9966/bench/versions/#Layout) no longer work after #9217 (cc @kkaefer) — they're now trying to load URLs of the form https://api.mapbox.com/v4/v4/... (duplicate prefix), which eventually causes JS errors. I confirmed that reverting that PR makes benchmarks work again.

Marking as a release blocker since we need to make sure this is not an edge case that manifests for users, outside of benchmarks (which might just be a symptom).

[mourner]

A workaround for running benchmarks until this is fixed (run in the benchmarked branch):

git revert --no-commit 77cfc5c135fa23a432e065e286326cfe87b2400d