Remove duplicate dependency (#4407)

This dependency is required in both require and require-dev section,
which can lead to unexpected behavior.

composer.json

@@ -23,7 +23,7 @@
         "knplabs/knp-menu-bundle": "^2.1.1",
         "sonata-project/block-bundle": "^3.2",
         "sonata-project/core-bundle": "^3.1",
-        "sonata-project/exporter": "^1.0",
+        "sonata-project/exporter": "^1.7",
         "symfony/class-loader": "^2.3 || ^3.0",
         "symfony/config": "^2.3.9 || ^3.0",
         "symfony/console": "^2.3 || ^3.0",
@@ -48,7 +48,6 @@
         "matthiasnoback/symfony-dependency-injection-test": "^0.1 || ^1.0",
         "sensio/generator-bundle": "^2.3 || ^3.0",
         "sllh/php-cs-fixer-styleci-bridge": "^2.0",
-        "sonata-project/exporter": "^1.7",
         "sonata-project/intl-bundle": "^2.2.4",
         "symfony/phpunit-bridge": "^2.7 || ^3.0",
         "symfony/yaml": "^2.3 || ^3.0"