Merge bitcoin#14770: travis: Do not specify sudo in .travis

feeef7d Do not specify sudo in .travis (Julian Fleischer)

Pull request description:

  Travis is deprecating the `sudo` keyword and moves everything to
  the same infrastructure (sudo really selects between two infrastructures).

  See https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration?utm_source=in-app&utm_medium=intercom for more info.

Tree-SHA512: 3364fbeaf7af5e91ef97cf7fbcc75427ecb4e10b02a31cbc17ccc46a6077bba7a000539717bb6a351c404a2b408af7de6c4587089b02367e67e1c8bfd8fe69d1

.travis.yml

@@ -2,7 +2,6 @@
 # - sudo/dist/group are set so as to get Blue Box VMs, necessary for [loopback]
 #   IPv6 support
 
-sudo: required
 dist: bionic
 
 os: linux
@@ -203,7 +202,6 @@ after_success:
 # lint stage
     - stage: lint
       env:
-      sudo: false
       cache: false
       language: python
       python: '3.6'