Fix typo in proposal header

[shaun-nx]

Proposed changes

Corrects a typo in the header of the AuthenticationFilter proposal

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.13%. Comparing base (9af2858) to head (09bdf6e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4364      +/-   ##
==========================================
- Coverage   86.15%   86.13%   -0.03%     
==========================================
  Files         132      132              
  Lines       14343    14343              
  Branches       35       35              
==========================================
- Hits        12357    12354       -3     
- Misses       1784     1786       +2     
- Partials      202      203       +1     

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