Rust/poker: False positive test results when ranking triplets/pairs

When ranking triplets/pairs, the student might fail to compare the triplets’/pairs’ ranks first, and instead just compare individual highest cards’ ranks.
Some triplet/pair ranking tests don’t catch that error but it’s an easy fix.
Simply ensure that the losing hand’s lone card has a higher rank than the winning hand’s strongest multiple.

It looks like Rust syncs that exercise from the problem spec. Changes should do to the spec first and then be synced from the spec to the various tracks.

Prior to sending a PR for problem spec changes, you should start a discussion on the forum explaining what can use changing and why, and get some buy in from maintainers.