fix TestMethodForPlatformAttribute

replace Execute with ExecuteAsync and fix MSTEST0057

https://learn.microsoft.com/en-us/dotnet/core/testing/mstest-analyzers/mstest0057 (link currently dead)

Author: mus65

test/Renci.SshNet.Tests/Common/TestMethodForPlatformAttribute.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
@@ -8,18 +10,18 @@ namespace Renci.SshNet.Tests.Common
     [AttributeUsage(AttributeTargets.Method)]
     public sealed class TestMethodForPlatformAttribute : TestMethodAttribute
     {
-        public TestMethodForPlatformAttribute(string platform)
+        public TestMethodForPlatformAttribute(string platform, [CallerFilePath] string callerFilePath = "", [CallerLineNumber] int callerLineNumber = -1) : base(callerFilePath, callerLineNumber)
         {
             Platform = platform;
         }
 
         public string Platform { get; }
 
-        public override TestResult[] Execute(ITestMethod testMethod)
+        public override async Task<TestResult[]> ExecuteAsync(ITestMethod testMethod)
         {
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Create(Platform)))
             {
-                return base.Execute(testMethod);
+                return await base.ExecuteAsync(testMethod);
             }
 
             var message = $"Test not executed. The test is intended for the '{Platform}' platform only.";