Bugfixed compatibility tests in Travis CI

Author: yann-eugone

.travis.yml

@@ -14,10 +14,6 @@ env:
 matrix:
   exclude:
     # Symfony >= 4.0 PHP requirement is ^7.1.3
-    - php: 5.6
-      env: SYMFONY_VERSION="4.0.*"
-    - php: 5.6
-      env: SYMFONY_VERSION="4.1-dev"
     - php: 7.0
       env: SYMFONY_VERSION="4.0.*"
     - php: 7.0