fix gated build failures in interpret-community due to captum installation issues from conda

[imatiach-msft]

fix gated build failures in interpret-community due to captum installation issues from conda

Getting errors in gated builds:

ImportError while importing test module '/Users/runner/work/1/s/tests/test_explanation_adapter.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/local/miniconda/envs/interp_community/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_explanation_adapter.py:9: in <module>
    from captum.attr import IntegratedGradients
E   ModuleNotFoundError: No module named 'captum'

We were seeing similar errors in the https://github.com/microsoft/responsible-ai-toolbox repository and a similar fix was applied there to move captum to pip install after a new version of pytorch was released:
microsoft/responsible-ai-toolbox#2435

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (31a3eb2) 87.70% compared to head (f18d7e6) 87.70%.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #589   +/-   ##
=======================================
  Coverage   87.70%   87.70%           
=======================================
  Files          62       62           
  Lines        4083     4083           
=======================================
  Hits         3581     3581           
  Misses        502      502           

Flag	Coverage Δ
unittests	87.70% <ø> (ø)

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