Specify dependency URL in consistent fashion (#194)

Author: gwynne

Package.swift

@@ -20,7 +20,7 @@ let package = Package(
             targets: ["Algorithms"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/apple/swift-numerics", from: "1.0.0"),
+        .package(url: "https://github.com/apple/swift-numerics.git", from: "1.0.0"),
     ],
     targets: [
         .target(