Sphinx 5.0 requires setting language

[tjtg]

Tests run against latest package versions failed due to newly released Sphinx 5.0.0 requiring the configuration file set language. The existing None value now results in a warning.

Testing:

• Ran tests and they passed OK

[codecov]

Codecov Report

Merging #1728 (3704b2e) into master (57f76c0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1728   +/-   ##
=======================================
  Coverage   98.01%   98.01%           
=======================================
  Files         112      112           
  Lines       10310    10310           
=======================================
  Hits        10105    10105           
  Misses        205      205           

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[thbom001]

What can I say when four characters in total are changed. This looks good, except it would have been nicer to have language = "to" :-)