* Use double-tilde for strikethrough in Markdown tests
The current dev version of commonmark has disabled single tilde for strikethrough: https://github.com/r-lib/commonmark/pull/33 Using double-tilde will make it consistent with Pandoc's Markdown (where single-tilde is for subscripts).
* Skip tests if commonmark is outdated
* Revert "Skip tests if commonmark is outdated"
This reverts commit 97bee20863.
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Co-authored-by: Carson Sievert <cpsievert1@gmail.com>
