av1: add missing sequence header field

[aler9]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 83.01%. Comparing base (6b50d9b) to head (92f0f7a).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/codecs/av1/sequence_header.go	72.72%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #166      +/-   ##
==========================================
- Coverage   83.03%   83.01%   -0.02%     
==========================================
  Files          79       79              
  Lines        7266     7276      +10     
==========================================
+ Hits         6033     6040       +7     
- Misses        896      898       +2     
- Partials      337      338       +1     

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