Fix reverse(p::Pair) on release-0.4

[zhmz90]

The same as PR #14246 which is added a "backport pending 0.4" label

[tkelman]

This works, though if you do a future backport commit I like to do git cherry-pick -x -e $SHA, which will automatically add a cross-reference to the original commit. The -e will open the commit message for editing, where I like to also add a "ref #14246" to indicate the PR the change originally came from. I will write all these backporting recommendations down over the holidays once my own personal issue #8839 is closed.

[yuyichao]

once my own personal issue #8839 is closed.

Should we track it here? =)

[zhmz90]

Thank you @tkelman , I will try it next time.