Sphinx Documentation Build Issue

[bpaul4]

Fixes/Addresses:

• Recently, test runs have been failing due to Sphinx documentation build errors:
  14 WARNING: Invalid configuration value found: 'language = None'. Update your configuration to a valid langauge code. Falling back to 'en' (English).
15 make: *** [Makefile:242: dummy] Error 1
16 Error: Process completed with exit code 2.
• The first warning is related to Sphinx Issue #10474 and PR #10481 where None was removed as a supported flag for the language entry. This update switches the flag to 'en' (the new default) to remove the warning.

Summary/Motivation:

Changes proposed in this PR:

Legal Acknowledgement

By contributing to this software project, I agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the copyright and license terms described in the LICENSE.md file at the top level of this directory.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 32.58%. Comparing base (0537a52) to head (2bc01d1).
Report is 101 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1035   +/-   ##
=======================================
  Coverage   32.58%   32.58%           
=======================================
  Files         161      161           
  Lines       35856    35856           
  Branches     6047     6047           
=======================================
  Hits        11685    11685           
  Misses      23246    23246           
  Partials      925      925           

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[ksbeattie]

LGTM