chore: deprecate method in symmetryutilities

[stevenhua0320]

@sbillinge ready to review. Since for the equalPositions and nullSpace method we don't have test before, I added the pytest at the end.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.03%. Comparing base (6a25991) to head (f93a859).
⚠️ Report is 1 commits behind head on v3.4.0.

Additional details and impacted files

@@            Coverage Diff             @@
##           v3.4.0     #167      +/-   ##
==========================================
+ Coverage   99.02%   99.03%   +0.01%     
==========================================
  Files          13       13              
  Lines        2041     2071      +30     
==========================================
+ Hits         2021     2051      +30     
  Misses         20       20              

Files with missing lines	Coverage Δ
tests/test_symmetryutilities.py	99.74% <100.00%> (+0.02%)	⬆️

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