Update proptest dependency version in Cargo.toml

- Bumped the `proptest` dependency from version 1.5 to 1.9 to leverage the latest features and improvements.
- This update ensures compatibility with recent changes and enhances the testing capabilities of the cache library.

Author: TKorr

Cargo.toml

@@ -53,7 +53,7 @@ rand_distr = "0.5"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 chrono = "0.4"
-proptest = "1.5"
+proptest = "1.9"
 arbitrary = { version = "1.4", features = ["derive"] }
 
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