Re-enable checking of assemblies with strong names

This removes the `UsesCodeSignedAssemblies()` switch in `CorePsPlatform`
and reverts the work-arounds skipping strong name checking.

test/csharp/test_CorePsPlatform.cs

@@ -27,12 +27,6 @@ namespace PSTests
             Assert.False(Platform.HasAmsi());
         }
 
-        [Fact]
-        public static void TestUsesCodeSignedAssemblies()
-        {
-            Assert.False(Platform.UsesCodeSignedAssemblies());
-        }
-
         [Fact]
         public static void TestHasDriveAutoMounting()
         {

test/csharp/test_MshSnapinInfo.cs

@@ -22,7 +22,7 @@ namespace PSTests
         public void TestReadCoreEngineSnapIn()
         {
             PSSnapInInfo pSSnapInInfo = PSSnapInReader.ReadCoreEngineSnapIn();
-            Assert.Contains("PublicKeyToken=null", pSSnapInInfo.AssemblyName);
+            Assert.Contains("PublicKeyToken=31bf3856ad364e35", pSSnapInInfo.AssemblyName);
         }
     }
 }