Update minimum version of code review tool to 1.0.0-alpha4.

This fixes build error "Class 'GrumPHP\Process\ProcessFactory' not found".

Author: pfrenssen

composer.json

@@ -12,7 +12,7 @@
         "composer/installers": "~1.2",
         "drush/drush": "~9.0",
         "drupal-composer/drupal-scaffold": "~2.2",
-        "openeuropa/code-review": "~1.0",
+        "openeuropa/code-review": "^1.0.0-alpha4",
         "openeuropa/task-runner": "^1.0.0-beta3",
         "webflo/drupal-core-require-dev": "~8.6"
     },