Address flake8 rst docstring issues

[eirikurj]

Purpose

This PR fixes flake8 RST warnings when flake8-rst-docstrings extension enabled.

Expected time until merged

Once docs build pass

Type of change

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (non-backwards-compatible fix or feature)
• [x] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no API changes)
• [x] Documentation update
• [ ] Maintenance update
• [ ] Other (please describe)

Testing

Checklist

• [x] I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• [ ] I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• [ ] I have run unit and regression tests which pass locally with my changes
• [ ] I have added new tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation

[codecov[bot]]

Codecov Report

Merging #190 (3e4e7dc) into main (41ffb0b) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #190   +/-   ##
=======================================
  Coverage   64.77%   64.77%           
=======================================
  Files          47       47           
  Lines       11951    11951           
=======================================
  Hits         7741     7741           
  Misses       4210     4210           

Impacted Files	Coverage Δ
pygeo/constraints/DVCon.py	71.72% <ø> (ø)
pygeo/parameterization/BaseDVGeo.py	66.66% <ø> (ø)
pygeo/parameterization/DVGeoCST.py	89.34% <ø> (ø)
pygeo/parameterization/DVGeoSketch.py	67.92% <ø> (ø)

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