Update .travis.yml

Co-Authored-By: Alexis Lefebvre <alexislefebvre@users.noreply.github.com>

Author: Simperfit

.travis.yml

@@ -29,7 +29,7 @@ matrix:
     - php: 7.3
       env: SYMFONY_VERSION="^4.1"
     - php: 7.3
-      env: SYMFONY_VERSION="^4.3@beta"
+      env: SYMFONY_VERSION="^4.3"
   allow_failures:
     - php: 7.2
       env: SYMFONY_VERSION="dev-master"