Fix typo in swapoff

[vilgotf]

Seems no one's noticed this in 4 years... First commit for me it is :D

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[JohnTitor]

Good catch, thanks!
@bors r+

[bors]

📌 Commit cbee28b has been approved by JohnTitor

[bors]

⌛ Testing commit cbee28b with merge 10d99b9...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-11, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13
Approved by: JohnTitor
Pushing 10d99b9 to master...