Removed old pot files

These files are not used as is, if we add locale pot files,
they will have different names (install-guide.pot instead of
openstack-install.pot etc).

Backport: stable/havana
Cherry-Picked from: https://review.openstack.org/52746
Change-Id: I4efc663d0caee2c8c68fad69e43a41386c1133e7
Remove obsolete files from Install Guide

These files were not used at all.

Cherry-Picked from: https://review.openstack.org/#/c/52762/
Change-Id: Ic53aed04a39b14f10fb4501e61dc0b94d23f76c6
backport: stable/havana
Merge "Removed old pot files" into stable/havana