travis-ci: Remove hooks for Travis CI (typically used with GitHub)

travis-ci: Remove hooks for Travis CI (typically used with GitHub)

These will get out of date pretty quickly, so better to remove them now
that GitLab CI is the documented and supported solution.

This was our first public CI system, used because it is cost-free
to Open Source projects and integrated with GitHub.

It has served it's purpose now.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Fri Dec 14 22:04:20 CET 2018 on sn-devel-144