remove duplicate entries under title guides in table of contents

right now, there are duplicate titles under contents --> guides
as shown in https://docs.openstack.org/devstack/latest/, although
they will forward to different pages, it is still a little confusing
for users. This change will hide toctree in guides.rst and users could
click links in page to jump to detail page to read more.

Change-Id: I2f3abeca7f56a3aedeabb48630ed2c61635b93cd

Author: jshen28

doc/source/guides.rst

@@ -10,6 +10,7 @@ Walk through various setups used by stackers
 
 .. toctree::
    :glob:
+   :hidden:
    :maxdepth: 1
 
    guides/single-vm