Use Identifiable#current_user in Api::ProjectsController#update

Previously this was using the `@current_user` instance variable.
However, I think this was working somewhat by accident - probably
because `authorize_resource` was calling `Identifiable#current_user` and
thus setting `@current_user`. I think it's safer to have an explicit
call to `Identifiable#current_user`.

Author: floehopper

app/controllers/api/projects_controller.rb

@@ -39,7 +39,7 @@ def create
     end
 
     def update
-      result = Project::Update.call(project: @project, update_hash: project_params, current_user: @current_user)
+      result = Project::Update.call(project: @project, update_hash: project_params, current_user:)
 
       if result.success?
         render :show, formats: [:json]