bump samples macos platform

Author: ktoso

Samples/JavaProbablyPrime/Package.swift

@@ -7,7 +7,7 @@ import PackageDescription
 let package = Package(
   name: "JavaProbablyPrime",
   platforms: [
-    .macOS(.v10_15),
+    .macOS(.v15),
   ],
 
   products: [

Samples/JavaSieve/Package.swift

@@ -42,7 +42,7 @@ let javaIncludePath = "\(javaHome)/include"
 let package = Package(
     name: "JavaSieve",
     platforms: [
-        .macOS(.v10_15),
+        .macOS(.v15),
     ],
     dependencies: [
         .package(name: "swift-java", path: "../../"),