Spelling and RTD build fixes for latest update of typos and sphinx_rtd_theme

[ksbeattie]

Fixes/Addresses:

Problems discovered in, but unrelated to PR #1242:

The typos package got smarter, so these are fixes to some newly discovered misspellings.
This also fixes a problem cause by a new release of the sphinx_rtd_theme.

Summary/Motivation:

Trying to not look like the abismal spellers that we are.

Changes proposed in this PR:

Legal Acknowledgement

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[bpaul4]

Thanks for fixing this, @ksbeattie!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 38.77%. Comparing base (f8188d2) to head (4a212b1).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1246      +/-   ##
==========================================
+ Coverage   38.75%   38.77%   +0.02%     
==========================================
  Files         164      164              
  Lines       37139    37139              
  Branches     6164     5722     -442     
==========================================
+ Hits        14392    14402      +10     
- Misses      21611    21612       +1     
+ Partials     1136     1125      -11     

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