travis: update Fedora versions

.travis.yml

@@ -5,9 +5,8 @@ python: '3.5'
 install: git clone https://github.com/QubesOS/qubes-builder ~/qubes-builder
 script: ~/qubes-builder/scripts/travis-build
 env:
- - DISTS_VM=fc24 USE_QUBES_REPO_VERSION=4.0 USE_QUBES_REPO_TESTING=1
- - DISTS_VM=fc25 USE_QUBES_REPO_VERSION=4.0 USE_QUBES_REPO_TESTING=1
  - DISTS_VM=fc26 USE_QUBES_REPO_VERSION=4.0 USE_QUBES_REPO_TESTING=1
+ - DISTS_VM=fc27 USE_QUBES_REPO_VERSION=4.0 USE_QUBES_REPO_TESTING=1
  - DISTS_VM=jessie USE_QUBES_REPO_VERSION=4.0 USE_QUBES_REPO_TESTING=1
  - DISTS_VM=stretch USE_QUBES_REPO_VERSION=4.0 USE_QUBES_REPO_TESTING=1