Fixed deprication warnings for Markdown extensions

[caronc]

Description:

Related issue (if applicable): n/a

Remove deprecation warnings surrounding Markdown extensions.

Checklist

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

```diff @@ 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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