web3swift-team#846: change minimum version of CryptoSwift dependency

The minimum version of 1.5.1 is too small. These changes resolve dependency conflicts that have the 'CryptoSwift' dependency within the SPM package

Package.swift

@@ -13,7 +13,7 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/attaswift/BigInt.git", from: "5.3.0"),
-        .package(url: "https://github.com/krzyzanowskim/CryptoSwift.git", from: "1.5.1")
+        .package(url: "https://github.com/krzyzanowskim/CryptoSwift.git", from: "1.8.0")
     ],
     targets: [
         .target(name: "secp256k1"),