chore: deprecate spacegroup method

[stevenhua0320]

@sbillinge ready to review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.17%. Comparing base (279d29d) to head (d2d6285).
⚠️ Report is 3 commits behind head on v3.4.0.

Additional details and impacted files

@@            Coverage Diff             @@
##           v3.4.0     #180      +/-   ##
==========================================
+ Coverage   99.16%   99.17%   +0.01%     
==========================================
  Files          15       15              
  Lines        2400     2439      +39     
==========================================
+ Hits         2380     2419      +39     
  Misses         20       20              

Files with missing lines	Coverage Δ
tests/test_p_cif.py	99.70% <100.00%> (+<0.01%)	⬆️
tests/test_spacegroups.py	98.73% <100.00%> (+0.73%)	⬆️
tests/test_symmetryutilities.py	99.83% <100.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[sbillinge]

looks good, thanks. If and when you make new tests, please try and make the pytest tests not unittest tests as a general rule.