remove postbuild branch triggers

[romanlutz]

Description

Now that //Build is over we can remove the postbuild branch-specific triggers from all pipelines.

Checklist

• I have added screenshots above for all UI changes.
• I have added e2e tests for all UI changes.
• Documentation was updated if it was needed.

[github-actions]

https://responsibleai.blob.core.windows.net/pullrequest/microsoft/responsible-ai-toolbox/romanlutz/remove_postbuild/dashboard/index.html

[codecov-commenter]

Codecov Report

Merging #1476 (a0156bb) into main (12fe368) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1476   +/-   ##
=======================================
  Coverage   87.15%   87.15%           
=======================================
  Files         104      104           
  Lines        4897     4897           
=======================================
  Hits         4268     4268           
  Misses        629      629           

Flag	Coverage Δ
unittests	87.15% <ø> (ø)

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