Translate DateTime.Date without type mapping in legacy mode (#3032)

Fixes #3031

(cherry picked from commit 10aebeb)

Author: roji

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlDateTimeMemberTranslator.cs

@@ -72,7 +72,7 @@ public NpgsqlDateTimeMemberTranslator(
             switch (instance?.TypeMapping)
             {
                 case NpgsqlTimestampTypeMapping:
-                case NpgsqlTimestampTzTypeMapping when NpgsqlTypeMappingSource.LegacyTimestampBehavior:
+                case { } when NpgsqlTypeMappingSource.LegacyTimestampBehavior:
                     return _sqlExpressionFactory.Function(
                         "date_trunc",
                         new[] { _sqlExpressionFactory.Constant("day"), instance! },
@@ -225,4 +225,4 @@ private SqlExpression GetDatePartExpression(
 
             _ => null
         };
-}
+}