Remove repeated tasks and generate a single file
We were generating a flat JSON file with license information of all dependencies. However, with https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2517 , we want to categorize them based on dependencies. We can do this either using a separate file (which has additional dependency relationship) or we can modify the existing code to generate a single file that has all the necessary information. This commit does the latter and can be reverted in case it is not needed.