Footnotes don't display properly under CommonMark

[steveklabnik]

This footnote generates different HTML under --enable-commonmark and not. Not only does this trigger what's effectively a spurious warning, but it doesn't render correctly either.

cc @QuietMisdreavus @GuillaumeGomez , marking this as p-high

[ollie27]

This was fixed by pulldown-cmark/pulldown-cmark#21 rustdoc just needs to update its version of pulldown-cmark.

[QuietMisdreavus]

The thread in that issue says it was released in 0.0.15. According to the lockfile we're pulling in 0.0.14 for rustdoc, but also 0.1.0 for mdbook. I'll see if i can update the dependency for rustdoc and pull it in.

[QuietMisdreavus]

#45421 updates Pulldown for rustdoc and fixes this.

[steveklabnik]

I am not sure this actually fixes the warnings, as they use different IDs and such.

I'm testing this locally right now though; expect an update in ~20 minutes