update dependency on swift-metrics (#16)

* update dependency on swift-metrics

motivation: be compatible with the newly released version of swift-metrics

Author: tomerd

Package.swift

@@ -22,7 +22,7 @@ let package = Package(
         .library(name: "StatsdClient", targets: ["StatsdClient"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/apple/swift-metrics.git", from: "1.0.0"),
+        .package(url: "https://github.com/apple/swift-metrics.git", "1.0.0" ..< "3.0.0"),
         .package(url: "https://github.com/apple/swift-nio.git", from: "2.0.0"),
     ],
     targets: [