Mark `env.{docname, parser}` as per-document attributes (#14232)

doc/extdev/envapi.rst

@@ -43,12 +43,12 @@ Build environment API
 
       Dictionary mapping docnames to the docutils node for their main title.
 
+   **Per-document attributes**
+
    .. autoattribute:: docname
 
    .. autoattribute:: parser
 
-   **Per-document attributes**
-
    .. attribute:: current_document
 
       Temporary data storage while reading a document.