Drop DAMA 6 (#900)

Author: jordisala1991

composer.json

@@ -41,7 +41,7 @@
         "twig/twig": "^2.14 || ^3.0"
     },
     "require-dev": {
-        "dama/doctrine-test-bundle": "^6.7 || ^7.0",
+        "dama/doctrine-test-bundle": "^7.0",
         "doctrine/doctrine-bundle": "^2.7",
         "doctrine/mongodb-odm": "^2.4",
         "doctrine/orm": "^2.14",