Fix Vision Capability Test for MacOS

[BeibinLi]

Why are these changes needed?

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.90%. Comparing base (c030225) to head (62033d7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2260      +/-   ##
==========================================
+ Coverage   37.94%   47.90%   +9.95%     
==========================================
  Files          77       77              
  Lines        7784     7784              
  Branches     1667     1805     +138     
==========================================
+ Hits         2954     3729     +775     
+ Misses       4580     3741     -839     
- Partials      250      314      +64     

Flag	Coverage Δ
unittest	14.36% <ø> (?)
unittests	46.86% <ø> (+8.92%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.