Remove x12 from main menu, but page still exists if needed and can be linked

Author: danamlewis

docs/index.rst

@@ -62,7 +62,6 @@ Note: *We do not recommend using a PDF version of this guide. The docs are updat
    :caption: Build Your Rig
 
    Installing OpenAPS <docs/Build Your Rig/OpenAPS-install>
-   512/712 pump users <docs/Build Your Rig/x12-users>
    Tell us you’re looping <docs/Build Your Rig/keeping-up-to-date>
 
 .. toctree::