Remove redundant primitive-key constraint for old Mono compatibility

Tomlet/TomlSerializationMethods.cs

@@ -371,14 +371,13 @@
         };
     }
 
-    // unmanaged + IConvertible is the closest I can get to expressing "primitives only"
 #if MODERN_DOTNET
 #if NET7_0_OR_GREATER
     [RequiresDynamicCode("The native code for underlying implementations of deserialize helper methods may not be available for a given type.")]
 #endif // NET7_0_OR_GREATER
-    private static Deserialize<Dictionary<TKey, TValue>> PrimitiveKeyedDictionaryDeserializerFor<TKey, [DynamicallyAccessedMembers(MainDeserializerAccessedMemberTypes)] TValue>(TomlSerializerOptions options) where TKey : unmanaged, IConvertible
+    private static Deserialize<Dictionary<TKey, TValue>> PrimitiveKeyedDictionaryDeserializerFor<TKey, [DynamicallyAccessedMembers(MainDeserializerAccessedMemberTypes)] TValue>(TomlSerializerOptions options)
 #else
-        private static Deserialize<Dictionary<TKey, TValue>> PrimitiveKeyedDictionaryDeserializerFor<TKey, TValue>(TomlSerializerOptions options) where TKey : unmanaged, IConvertible
+        private static Deserialize<Dictionary<TKey, TValue>> PrimitiveKeyedDictionaryDeserializerFor<TKey, TValue>(TomlSerializerOptions options)
 #endif
     {
         var valueDeserializer = GetDeserializer(typeof(TValue), options);
@@ -386,9 +385,9 @@
         return value =>
         {
             if (value is not TomlTable table)
                 throw new TomlTypeMismatchException(typeof(TomlTable), value.GetType(), typeof(Dictionary<TKey, TValue>));
 
             return table.Entries
                 .Where(entry =>
                 {
                     if (!type.IsEnum || !options.IgnoreInvalidEnumValues)
@@ -539,4 +538,4 @@
                 .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
         });
     }
-}
+}