Remove code fallback for web rate limiter Git path exclusion

Summary

Remove the code fallback introduced in 18.7 for the web rate limiter Git path exclusion.

Background

In 18.7, a code change was implemented to prevent double-throttling of authenticated Git HTTP requests. A fallback mechanism was included to ensure safe rollout.

Proposal

The fallback code can be safely removed in 18.8 after the feature has been validated in production.

Related

• #581142