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>

programs/btc_spv/Cargo.toml

@@ -16,7 +16,7 @@ num-traits = "0.2"
 serde = "1.0.104"
 serde_derive = "1.0.103"
 solana-sdk = { path = "../../sdk", version = "1.1.0"}
-hex = "0.3.2"
+hex = "0.4.2"
 
 [lib]
 crate-type = ["lib", "cdylib"]

programs/btc_spv_bin/Cargo.toml

@@ -13,7 +13,7 @@ clap="2.33.0"
 reqwest = { version = "0.10.1", default-features = false, features = ["blocking", "rustls-tls", "json"] }
 serde="1.0.104"
 serde_derive="1.0.103"
-hex = "0.3.2"
+hex = "0.4.2"
 
 [[bin]]
 name = "blockheaders"