Update eth_usd_feed.py

[0xSpuddy]

Summary

Steps Taken to QA Changes

Checklist

This pull request is:

• A documentation error, docs update, or typographical error fix
  • No tests or issue needed
• A code fix
  • Please reference the related issue by including "Closes <link to issue>" in this Pull Request's summary section.
    • If no issue exists, please create a bug report issue
  • Please include tests. Fixes without tests will not be accepted unless it's related to the documentation only.
  • Please make sure docs are updated if need be
• A feature implementation
  • Please reference the related issue by including "Closes <link to issue>" in this Pull Request's summary section.
    • If no issue exists, please create a feature enhancement issue
  • Please include tests
  • Please make sure docs updates are both thorough and easy to reproduce by somebody with limited knowledge of the feature that you are submitting

Happy engineering!