Add missing comma

src/content/chapter4_standard_library/lesson03_dict_module/en.html

@@ -35,6 +35,6 @@
 </p>
 <p>
   Dicts are unordered! If it appears that the items in a dict are in a certain
-  order this is incidental and should not be relied upon. Any ordering may
+  order, it is incidental and should not be relied upon. Any ordering may
   change without warning in future versions or on different runtimes.
 </p>