Fix path to dev script packages

The composer.json file is located under /dev-scripts. The documentation
suggests that the directory should be prefixed with a slash. We should
try to do so as well here.

.github/dependabot.yml

@@ -46,7 +46,7 @@ updates:
       - "dependencies"
       - "drupal"
   - package-ecosystem: composer
-    directory: "dev-scripts/"
+    directory: "/dev-scripts"
     open-pull-requests-limit: 2
     groups:
       minor-composer-dependencies: