Fix typo in ChatCompletionToolChoiceOption docs (#401)

Author: wtdcode

async-openai/src/types/chat.rs

@@ -542,7 +542,7 @@ pub struct ChatCompletionNamedToolChoice {
 /// `required` means the model must call one or more tools.
 /// Specifying a particular tool via `{"type": "function", "function": {"name": "my_function"}}` forces the model to call that tool.
 ///
-/// `none` is the default when no tools are present. `auto` is the default if tools are present.present.
+/// `none` is the default when no tools are present. `auto` is the default if tools are present.
 #[derive(Clone, Serialize, Default, Debug, Deserialize, PartialEq)]
 #[serde(rename_all = "lowercase")]
 pub enum ChatCompletionToolChoiceOption {