Update documentation and website with the License Compliance term

We are renaming License Management to License Compliance (see &659 (closed)).

We need to update the front end text and references in documentation and website to reflect the new name.

1. Change frontend text: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15163
2. Screenshots https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/32537
3. Change Docs https://gitlab.com/gitlab-org/gitlab-ce/issues/63329
4. @NicoleSchwartz: Change handbook and website - MR: gitlab-com/www-gitlab-com!27448 (merged)