Out of sync practice exercises

[github-actions]

Out of sync practice exercises have been detected:

Command: configlet sync --tests --docs --metadata --filepaths

Output:

Checking exercises...
[warn] metadata: unsynced: allergies
[warn] metadata: unsynced: bob
[warn] metadata: unsynced: etl
[warn] metadata: unsynced: gigasecond
[warn] metadata: unsynced: kindergarten-garden
[warn] metadata: unsynced: matrix
[warn] metadata: unsynced: phone-number
[warn] metadata: unsynced: pig-latin
[warn] metadata: unsynced: reverse-string
[warn] metadata: unsynced: space-age
[warn] metadata: unsynced: triangle
[warn] perfect-numbers: missing 1 test case
       - Abundant numbers -> Perfect square abundant number is classified correctly (05f15b93-849c-45e9-9c7d-1ea131ef7d10)
[warn] satellite: missing 3 test cases
       - A degenerate binary tree (af31ae02-7e5b-4452-a990-bccb3fca9148)
       - Another degenerate binary tree (ee54463d-a719-4aae-ade4-190d30ce7320)
       - Tree with many more items (87123c08-c155-4486-90a4-e2f75b0f3e8f)
[warn] some exercises have unsynced metadata
[warn] some exercises are missing test cases

[keiravillekode]

PRs to add the missing test cases:

#510

#507