Fixed deprication warnings for Markdown extensions

[caronc]

Description:

Related issue (if applicable): n/a

Remove deprecation warnings surrounding Markdown extensions.

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.27%. Comparing base (cced5ed) to head (c4f379e).
Report is 2 commits behind head on master.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1108   +/-   ##
=======================================
  Coverage   99.27%   99.27%           
=======================================
  Files         139      139           
  Lines       18029    18029           
  Branches     3680     3680           
=======================================
  Hits        17899    17899           
  Misses        121      121           
  Partials        9        9           

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