Remove platform tests

This is pointless to test as the .NET Code better be correct, or we have
worse problems.

test/csharp/test_CorePsPlatform.cs

@@ -9,18 +9,6 @@ namespace PSTests
     [Collection("AssemblyLoadContext")]
     public static class PlatformTests
     {
-        [Fact]
-        public static void TestIsLinux()
-        {
-            Assert.True(Platform.IsLinux);
-        }
-
-        [Fact]
-        public static void TestIsWindows()
-        {
-            Assert.False(Platform.IsWindows);
-        }
-
         [Fact]
         public static void TestIsCore()
         {