cleanup travis.yml

[d-m-u]

per https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration: If you currently specify sudo: false in your .travis.yml, we recommend removing that configuration soon...

[miq-bot]

Checked commit https://github.com/d-m-u/azure-armrest/commit/0c4dab65ea8afb1ccfe9c1ab7b84deefe4eb19dd with ruby 2.6.3, rubocop 0.69.0, haml-lint 0.28.0, and yamllint 1 file checked, 1 offense detected

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• [ ] :bomb: :boom: :fire: :fire_engine: - Linter/Yaml - missing config files

[djberg96]

LGTM.