🚨 configlet sync --test found unsynced tests

```
Checking exercises...
[warn] bob: missing 2 test cases
- multiple line question (2c7278ac-f955-4eb4-bf8f-e33eb4116a15)
- shouting a statement containing a question mark (3c954328-86fb-4c71-8961-e18d6a5e2517)
[warn] flower-field: missing 1 test case
- multiple adjacent flowers (6e4ac13a-3e43-4728-a2e3-3551d4b1a996)
[warn] forth: missing 6 test cases
- addition -> more than two values on the stack (1e07a098-c5fa-4c66-97b2-3c81205dbc2f)
- subtraction -> more than two values on the stack (2c8cc5ed-da97-4cb1-8b98-fa7b526644f4)
- multiplication -> more than two values on the stack (5cd085b5-deb1-43cc-9c17-6b1c38bc9970)
- division -> more than two values on the stack (f224f3e0-b6b6-4864-81de-9769ecefa03f)
- combined arithmetic -> multiplication and addition (f749b540-53aa-458e-87ec-a70797eddbcb)
- combined arithmetic -> addition and multiplication (c8e5a4c2-f9bf-4805-9a35-3c3314e4989a)
[warn] isbn-verifier: missing 2 test cases
- only one check digit is allowed (8005b57f-f194-44ee-88d2-a77ac4142591)
- X is not substituted by the value 10 (fdb14c99-4cf8-43c5-b06d-eb1638eff343)
[warn] largest-series-product: missing 2 test cases
- rejects span longer than string length (0ae1ce53-d9ba-41bb-827f-2fceb64f058b)
- rejects empty string and nonzero span (6cf66098-a6af-4223-aab1-26aeeefc7402)
[warn] perfect-numbers: missing 1 test case
- Abundant numbers -> Perfect square abundant number is classified correctly (05f15b93-849c-45e9-9c7d-1ea131ef7d10)
[warn] pig-latin: missing 1 test case
- first letter and ay are moved to the end of words that start with consonants -> word beginning with consonant and vowel containing qu (e59dbbe8-ccee-4619-a8e9-ce017489bfc0)
[warn] two-bucket: missing 2 test cases
- Measure using bucket one much bigger than bucket two (58d70152-bf2b-46bb-ad54-be58ebe94c03)
- Measure using bucket one much smaller than bucket two (9dbe6499-caa5-4a58-b5ce-c988d71b8981)
[warn] some exercises are missing test cases
```

`configlet sync --test` を実行し、その出力を bob、flower-field、forth、isbn-verifier、largest-series-product、perfect-numbers、pig-latin、two-bucket のチェックリストとして使用します。各 exercise の既存のテストファイルを確認し、一覧にある不足しているケースを追加します。コマンドが同期されていないテストを報告しなくなれば完了です。

索引モデルが issue の本文から書いたものです。