Footnotes only render first line of content

Description

The docs site currently ignores all content on new lines within a footnote. This bug is not present elsewhere (such as the wiki or issues or rendering of markdown within a repo).

Steps to reproduce

https://docs.gitlab.com/ee/user/markdown.html#footnotes

The markdown block uses multiple lines to avoid an awkward non-wrapped long line in the verbatim code.

Actual result

The rendered footnote includes only the first line from the markdown, and the later lines get rendered as regular non-footnote content.

Expected result

The whole paragraph should be within the footnote, as shown correctly at https://gitlab.com/gitlab-org/gitlab/blob/master/doc/user/markdown.md#footnotes

Further details

A workaround could show the same verbatim code block but put the behind-the-scenes code-to-render all on a single line. That might be enough since perhaps there are no other uses of footnotes within docs.gitlab.com, but that would not actually be a bug fix.