[swift] update Swift4 samples (#4589)

* swift-update

* dont put swift4 in ensure-up-to-date

samples/client/petstore/swift4/promisekitLibrary/Package.swift

@@ -9,12 +9,12 @@ let package = Package(
         // Products define the executables and libraries produced by a package, and make them visible to other packages.
         .library(
             name: "PetstoreClient",
-            targets: ["PetstoreClient"]),
+            targets: ["PetstoreClient"])
     ],
     dependencies: [
         // Dependencies declare other packages that this package depends on.
         .package(url: "https://github.com/Alamofire/Alamofire.git", from: "4.9.0"),
-        .package(url: "https://github.com/mxcl/PromiseKit.git", from: "6.11.0"),
+        .package(url: "https://github.com/mxcl/PromiseKit.git", from: "6.11.0")
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
@@ -23,6 +23,6 @@ let package = Package(
             name: "PetstoreClient",
             dependencies: ["Alamofire", "PromiseKit"],
             path: "PetstoreClient/Classes"
-        ),
+        )
     ]
 )