gh-101777: Make `PriorityQueue` docs slightly clearer (GH-102026)

Adjust wording slightly, and use min(entries) instead of
sorted(list(entries))[0] as an example.
(cherry picked from commit 350ba7c07f8983537883e093c5c623287a2a22e5)

Co-authored-by: Owain Davies <116417456+OTheDev@users.noreply.github.com>