fix(toxav): pass video bit rate as kbit

[Green-Sky]

Previously we unintentionally made it Mbit.

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This change is 

[Green-Sky]

every client assumes kbits (as they should):

• toxic: https://github.com/JFreegman/toxic/blob/b5af9279ed9faff0330a6a2710ca80a805f3c074/src/video_call.c#L28
• qtox: https://github.com/qTox/qTox/blob/8632be21bebfa9ece815c3af4e298b775f50c85e/src/core/coreav.h#L134
• utox: https://github.com/uTox/uTox/blob/ce4b44a10b5a9866f4be852b8dcbcb264ab6cd01/src/av/video.h#L12-L13
• all the zoff stuff (and his fork already fixed this issue)
• Seers Lodge: https://gitlab.com/nand-apps/seers-lodge/-/blob/main/composeApp/src/commonMain/kotlin/nand/apps/chat/engine/tox/ToxChatEngine.kt#L60
• probably more...

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tomato currently assumes Mbits, but only because I know about this bug.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.96%. Comparing base (5f97890) to head (fa723e3).
Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2782      +/-   ##
==========================================
- Coverage   73.04%   72.96%   -0.08%     
==========================================
  Files         149      149              
  Lines       30478    30566      +88     
==========================================
+ Hits        22263    22303      +40     
- Misses       8215     8263      +48     

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