Exclude ClearTests from SPM test target

The ClearTests attempt to clear the entire keychain of the OS that `swift test` is running on. At best, keychain permissions prevents this from working, and at worst, important keychain items can be deleted.

Package.swift

@@ -10,6 +10,10 @@ let package = Package(
     ],
     targets: [
         .target(name: "KeychainSwift", dependencies: [], path: "Sources"),
-        .testTarget(name: "KeychainSwiftTests", dependencies: ["KeychainSwift"])
+        .testTarget(
+            name: "KeychainSwiftTests", 
+            dependencies: ["KeychainSwift"],
+            exclude: ["ClearTests.swift"]
+        )
     ]
 )