Don't claim NTLM support on Browser

Author: filipnavara

src/libraries/Common/tests/System/Net/Capability.Security.Unix.cs

@@ -7,7 +7,7 @@ public static partial class Capability
     {
         public static bool IsNtlmInstalled()
         {
-            return true;
+            return !OperatingSystem.IsBrowser();
         }
     }
 }