travis: Remove unused sudo:false

Builds in sudo-disabled docker containers are no longer available as of
last year and all builds happen on sudo enabled vms.

https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration#timeline---its-happening-fast

Author: MarcoFalke

.travis.yml

@@ -1,6 +1,5 @@
 os: linux
 language: generic
-sudo: false
 script:
     - scripts/link-format-chk.sh
     - scripts/buildtable.pl >/tmp/table.mediawiki || exit 1