nit: remove redundant CreateGuildRoleParams

CreateGuildRoleParams is identical to ModifyGuildRoleParams, so just use
the latter when creating new roles.

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -264,7 +264,7 @@ namespace Discord.Rest
         {
             if (name == null) throw new ArgumentNullException(paramName: nameof(name));
 
-            var createGuildRoleParams = new API.Rest.CreateGuildRoleParams
+            var createGuildRoleParams = new API.Rest.ModifyGuildRoleParams
             {
                 Color = color?.RawValue ?? Optional.Create<uint>(),
                 Hoist = isHoisted,