[System.Management] change the term "corefx" to ".NET Framework"

dotnet#118369

Author: Yoticc

src/libraries/System.Management/tests/System/Management/ManagementDateTimeConverterTests.cs

@@ -15,7 +15,7 @@ public void DateTime_RoundTrip()
             // Additional skip if the testing platform does not support ActiveIssue
             if (PlatformDetection.IsNetFramework)
             {
-                throw new SkipTestException("Incorrect logic for corefx implementation");
+                throw new SkipTestException("Incorrect logic for .NET Framework implementation");
             }
 
             var date = new DateTime(2002, 4, 8, 14, 18, 35, 978, DateTimeKind.Utc).AddMinutes(150);