remove sudo: in .travis.yml

https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration

Committed via https://github.com/asottile/all-repos

Author: asottile

.travis.yml

@@ -1,13 +1,11 @@
 language: python
-sudo: false
 matrix:
     include:  # These should match the tox env list
     -   env: TOXENV=py27
     -   env: TOXENV=py36
         python: 3.6
     -   env: TOXENV=py37
         python: 3.7
-        sudo: required
         dist: xenial
     -   env: TOXENV=pypy
         python: pypy-5.7.1