Fix detection of IDependencyMap impl

Not pretty, but it works.

src/Discord.Net.Commands/Utilities/ReflectionUtils.cs

@@ -58,7 +58,7 @@ namespace Discord.Commands
             {
                 if (targetType == typeof(CommandService))
                     arg = service;
-                else if (targetType == typeof(IDependencyMap))
+                else if (targetType.GetTypeInfo().ImplementedInterfaces.Contains(typeof(IDependencyMap)))
                     arg = map;
                 else
                     throw new InvalidOperationException($"Failed to create \"{baseType.FullName}\", dependency \"{targetType.Name}\" was not found.");