travis: bump dom0 to fedora-25

.travis.yml

@@ -11,7 +11,7 @@ script:
   - ./run-tests --no-syslog
   - ~/qubes-builder/scripts/travis-build
 env:
- - DIST_DOM0=fc23 USE_QUBES_REPO_VERSION=3.2 USE_QUBES_REPO_TESTING=1
+ - DIST_DOM0=fc25 USE_QUBES_REPO_VERSION=3.2 USE_QUBES_REPO_TESTING=1
 
 after_success:
   - ~/qubes-builder/scripts/travis-deploy