Bump hex from 0.4.1 to 0.4.2 (#8725)

Bumps [hex](https://github.com/KokaKiwi/rust-hex) from 0.4.1 to 0.4.2.
- [Release notes](https://github.com/KokaKiwi/rust-hex/releases)
- [Commits](https://github.com/KokaKiwi/rust-hex/compare/v0.4.1...v0.4.2)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

merkle-tree/Cargo.toml

@@ -13,7 +13,7 @@ solana-sdk = { path = "../sdk", version = "1.1.0" }
 fast-math = "0.1"
 
 [dev-dependencies]
-hex = "0.4.0"
+hex = "0.4.2"
 
 [lib]
 crate-type = ["lib"]