kamailio-kemi-framework: use nav instead of pages in mkdocs.yml

kamailio-kemi-framework/mkdocs.yml

@@ -1,7 +1,7 @@
 site_name: Kamailio KEMI Framework
 theme: readthedocs
 extra_css: [extra.css]
-pages:
+nav:
     - 'Kamailio KEMI Framework': 'index.md'
     - 'KEMI Interpreters': 'kemi.md'
     - 'Core And PV Functions': 'core.md'