Move `/licenses` api endpoint to `/templates/licenses`
Related to gitlab-org/gitlab-ce#14106
In EE we now have somewhat ambiguous API endpoints. /license
refers to the EE license while /licenses
(plural) refers to license templates. @DouweM mentioned that we're adding .gitignore
templates in gitlab-org/gitlab-ce#14106 so it may make sense to add a /templates
namespace. Then, move the /license
templates endpoint to be underneath, along with .gitignore
endpoints.