Remove sudo: required from .travis.yml (facebook#37)

Summary:
This is just facebookarchive/bistro#37, backported to `fbcode_builder`.

snarkmaster
Pull Request resolved: facebookarchive/bistro#37

Test Plan: Push and watch Travis

Reviewed By: simpkins

Differential Revision: D16453080

Pulled By: snarkmaster

fbshipit-source-id: a15eaead931f046c41e50f8e3b412ef68b172d65

.travis.yml

@@ -1,8 +1,6 @@
 # Facebook projects that use `fbcode_builder` for continuous integration
 # share this Travis configuration to run builds via Docker.
 
-sudo: required
-
 # Docker disables IPv6 in containers by default. Enable it for unit tests that need [::1].
 before_script:
   - if [[ "$TRAVIS_OS_NAME" != "osx" ]];