Remove tools/generate-hot-reference.sh
Remove tools/generate-hot-reference.sh

As per https://bugs.launchpad.net/openstack-manuals/+bug/1469606 ,
the HOT Regerence Guide has been removed.
Therefore, remove tools/generate-hot-reference.sh.

* remove tools/generate-hot-reference.sh

Change-Id: If11d3b051b8d46a0ba41f40f6c8cb9069191334d

openstack/openstack-manuals,potsmaster/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,kairoaraujo/openstack-manuals,openstack/openstack-manuals,potsmaster/openstack-manuals,kairoaraujo/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,saeki-masaki/openstack-manuals,Akasurde/openstack-manuals