Escape square brackets in doc comment

src/protocol/frame/coding.rs

@@ -143,7 +143,7 @@ pub enum CloseCode {
     Abnormal,
     /// Indicates that an endpoint is terminating the connection
     /// because it has received data within a message that was not
-    /// consistent with the type of the message (e.g., non-UTF-8 [RFC3629]
+    /// consistent with the type of the message (e.g., non-UTF-8 \[RFC3629\]
     /// data within a text message).
     Invalid,
     /// Indicates that an endpoint is terminating the connection