Travis CI: add 69lts to the list of branches to be checked

This basically means that any pushes to the 69lts branch will also
generate a new Travis CI job.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

.travis.yml

@@ -22,6 +22,7 @@ branches:
     only:
         - master
         - 52lts
+        - 69lts
 
 cache:
     directories: