fix nightly pytorch error on macos by installing numpy from conda

[imatiach-msft]

rely on installing numpy from conda - otherwise we see segfaults on macos when installing pytorch and lightgbm together:

/Users/runner/work/_temp/166c9a15-3b69-4e3f-a25e-1b51a6c0154c.sh: line 2: 13956 Segmentation fault: 11  python -m pytest tests/ -m "not notebooks" --junitxml=./TEST--TEST.xml -o junit_suite_name="MacOS Unit 3.7-Unit"

Update - see passing nightly build here:
https://dev.azure.com/responsibleai/interpret-community/_build/results?buildId=14736&view=results

[codecov-commenter]

Codecov Report

Merging #535 (0232244) into main (4970f08) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #535   +/-   ##
=======================================
  Coverage   87.63%   87.63%           
=======================================
  Files          62       62           
  Lines        4077     4077           
=======================================
  Hits         3573     3573           
  Misses        504      504           

Flag	Coverage Δ
unittests	87.63% <ø> (ø)

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