Remove Kramdown patch and update to v2.3.1 gem
As of !56750 (merged), Markdown should no longer be rendered through Kramdown for Wiki pages. The monkey patch can be removed with Kramdown v2.3.1 since https://github.com/gettalong/kramdown/pull/708 has been merged.
Diff: https://my.diffend.io/gems/kramdown/2.3.0/2.3.1
Relates to #324452 (closed)
Edited by Stan Hu