add 1.5 version to 404 page

(cherry picked from commit 14e9078)

Author: rebortg

docs/404.rst

@@ -8,4 +8,5 @@ Try using the search box or go to the release homepage:
 
   * `1.2.x (crux) <https://docs.vyos.io/en/crux/>`_
   * `1.3.x (equuleus) <https://docs.vyos.io/en/equuleus/>`_
-  * `rolling release (sagitta) <https://docs.vyos.io/en/latest/>`_
+  * `1.4.x (sagitta) <https://docs.vyos.io/en/sagitta/>`_
+  * `rolling release (circinus) <https://docs.vyos.io/en/latest/>`_