Fix pdf-doc build by skiping the sample file
Fix pdf-doc build by skiping the sample file

Tempest pdf doc build includes the sample config
file which is large in size and end up with
error 'Dimension too large'

- https://zuul.opendev.org/t/openstack/build/84d73ec987d04c05acc54b231d33067e/log/sphinx-build-pdf.log#1874

Its happening while adding new config option in
https://review.opendev.org/#/c/686073/ which means we
are at the edge of pdf build limit.

We should not include the sample config file as part
of pdf build.

Change-Id: I59383505989705d35d86b19b5c1aaafebd2bd307
Closes-Bug: #1886212

openstack/tempest,openstack/tempest