Remove back-compat code that's not needed anymore

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/helpers/projects_helper.rb

@@ -124,11 +124,7 @@ module ProjectsHelper
   end
 
   def license_short_name(project)
-    no_license_key = project.repository.license_key.nil? ||
-      # Back-compat if cache contains 'no-license', can be removed in a few weeks
-      project.repository.license_key == 'no-license'
-
-    return 'LICENSE' if no_license_key
+    return 'LICENSE' if project.repository.license_key.nil?
 
     license = Licensee::License.new(project.repository.license_key)