Use backticks

Author: Michael Lenahan

reference/forms/types/options/choice_value.rst.inc

@@ -14,8 +14,8 @@ configure the value that will be sent in the API request).
 This can be a callable or a property path. See `choice_label`_ for similar usage.
 If ``null`` is used, an incrementing integer is used as the name.
 
-If you are using a callable to populate choice_value, you need to check for the
-case that the value of the field may be null.
+If you are using a callable to populate ```choice_value```, you need to check
+for the case that the value of the field may be ```null```.
 
 .. caution::