Cleanup deprecated header handling

[elacuesta]

Removing deprecated header handling as per the current deprecation policy.

Deprecated on v0.0.41, almost one and a half years ago.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.55%. Comparing base (e7dbf9c) to head (70cab80).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #362      +/-   ##
==========================================
+ Coverage   92.40%   99.55%   +7.15%     
==========================================
  Files           6        6              
  Lines         685      680       -5     
==========================================
+ Hits          633      677      +44     
+ Misses         52        3      -49     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.