Model overview: bold cohort names in tooltip

[romanlutz]

Description

This change makes cohort names bold in all tooltips within Model Overview to make sure they're easy to spot.

Before:

After:

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/bold_cohort_tooltip/dashboard/index.html

[codecov-commenter]

Codecov Report

Merging #1531 (6b44d6e) into main (5f90591) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1531   +/-   ##
=======================================
  Coverage   87.73%   87.73%           
=======================================
  Files         109      109           
  Lines        5260     5260           
=======================================
  Hits         4615     4615           
  Misses        645      645           

Flag	Coverage Δ
unittests	87.73% <ø> (ø)

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[github-actions]

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