Close Challenge 9 (#224)

Resolves #72

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Author: cvick32

doc/src/challenges/0009-duration.md

@@ -1,14 +1,13 @@
 # Challenge 9: Safe abstractions for `core::time::Duration`
 
-- **Status:** Open
+- **Status:** Resolved
 - **Tracking Issue:** [#72](https://github.com/model-checking/verify-rust-std/issues/72)
 - **Start date:** *2024/08/20*
-- **End date:** *2025/04/10*
+- **End date:** *2024/12/10*
 - **Reward:** *N/A*
-
+- **Contributors**: [Samuel Thomas](https://github.com/sgpthomas) and [Cole Vick](https://github.com/cvick32)
 -------------------
 
-
 ## Goal
 
 Write function contracts for `core::time::Duration` that can be used as safe abstractions.