feat: Imported Firefox 89.0b8 API schema

[rpl]

This PR contains only a small change related to the schema definition for the toolbar color toolbar_field_separator, which has been deprecated because isn't used anywhere in the Proton UI.

[codecov]

Codecov Report

Merging #3710 (5aade90) into master (4e1db37) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3710   +/-   ##
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  Coverage   98.87%   98.87%           
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  Files          52       52           
  Lines        1860     1860           
  Branches      393      393           
=======================================
  Hits         1839     1839           
  Misses         21       21           

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[willdurand]

I am preparing a new version so I am going to merge this patch myself since it has been approved.