chore: fix missing part (#739)

Author: Lightning00Blade

index.bs

@@ -6238,7 +6238,7 @@ The [=remote end steps=] given |session| and |command parameters| are:
 
   1. Let |cookie header| be an empty [=byte sequence=].
 
-  1. For each |cookie| in |command parameters|:
+  1. For each |cookie| in |command parameters|["<code>cookies</code>"]:
 
     1. If |cookie header| is not empty, append `<code>;</code>` to |cookie
        header|.