Update swift-tools-version in newly created packages to 5.3. This only affects swift init.

The existing unit test `testInitManifest` checks that the manifest of the instantiated package has the updated version number.

rdar://63365232

Author: abertelrud

Sources/Workspace/InitPackage.swift

@@ -14,7 +14,7 @@ import PackageModel
 /// Create an initial template package.
 public final class InitPackage {
     /// The tool version to be used for new packages.
-    public static let newPackageToolsVersion = ToolsVersion(version: "5.2.0")
+    public static let newPackageToolsVersion = ToolsVersion(version: "5.3.0")
 
     /// Options for the template package.
     public struct InitPackageOptions {