docs(http): document mutable guild features

Discord only allows the `COMMUNITY`, `DISCOVERABLE` and `INVITES_DISABLED` features to be edited manually.

Reference: discord/discord-api-docs#5270

twilight-http/src/request/guild/update_guild.rs

@@ -164,8 +164,16 @@ impl<'a> UpdateGuild<'a> {
     ///
     /// Attempting to add or remove the `COMMUNITY` feature requires the
     /// [`Permissions::ADMINISTRATOR`] permission.
+    /// 
+    /// Attempting to add or remove the `INVITES_DISABLED` feature requires
+    /// the [`Permissions::MANAGE_GUILD`] permission.
+    /// 
+    /// Attempting to add or remove the `DISCOVERABLE` feature requires
+    /// the [`Permissions::ADMINISTRATOR`] permission. Additionally the guild
+    /// must pass all the discovery requirements.
     ///
     /// [`Permissions::ADMINISTRATOR`]: twilight_model::guild::Permissions::ADMINISTRATOR
+    /// [`Permissions::MANAGE_GUILD`]: twilight_model::guild::Permissions::MANAGE_GUILD
     pub const fn features(mut self, features: &'a [&'a str]) -> Self {
         self.fields.features = Some(features);