remove unused func test category exclusion

When the temporary clear() calls were removed from the
functional test category lists in PR microsoft#50 (see commit
7e67496), this following
block to re-exclude tests marked MacOnly became redundant,
so we can remove it now.

Scalar.FunctionalTests/Program.cs

@@ -102,11 +102,6 @@ public static void Main(string[] args)
             // with the non-virtualized solution
             excludeCategories.Add(Categories.NeedsUpdatesForNonVirtualizedMode);
 
-            if (!RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
-            {
-                excludeCategories.Add(Categories.MacOnly);
-            }
-
             ScalarTestConfig.RepoToClone =
                 runner.GetCustomArgWithParam("--repo-to-clone")
                 ?? Properties.Settings.Default.RepoToClone;