Update PersonalDataAttribute.cs (dotnet#36067)

Author: HaoK

src/Identity/Extensions.Core/src/PersonalDataAttribute.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Identity
     /// <summary>
     /// Used to indicate that a something is considered personal data.
     /// </summary>
-    [AttributeUsage(AttributeTargets.All)]
+    [AttributeUsage(AttributeTargets.Property)]
     public class PersonalDataAttribute : Attribute
     { }
-}
+}