Fix test on MySql

Author: bahusoid

src/NHibernate.Test/Async/Linq/EnumTests.cs

@@ -48,7 +48,7 @@ protected override HbmMapping GetMappings()
 					rc.Property(x => x.NullableEnum, m =>
 					{
 						m.Type(_enumType);
-						m.Formula($"(case when Enum = {_unspecifiedValue} then null else Enum end)");
+						m.Formula($"(case when `Enum` = {_unspecifiedValue} then null else `Enum` end)");
 					});
 					rc.ManyToOne(x => x.Other, m => m.Cascade(Mapping.ByCode.Cascade.All));
 				});

src/NHibernate.Test/Linq/EnumTests.cs

@@ -35,7 +35,7 @@ protected override HbmMapping GetMappings()
 					rc.Property(x => x.NullableEnum, m =>
 					{
 						m.Type(_enumType);
-						m.Formula($"(case when Enum = {_unspecifiedValue} then null else Enum end)");
+						m.Formula($"(case when `Enum` = {_unspecifiedValue} then null else `Enum` end)");
 					});
 					rc.ManyToOne(x => x.Other, m => m.Cascade(Mapping.ByCode.Cascade.All));
 				});