Simplify SQL queries of marking a todo as done

CHANGELOG

@@ -131,6 +131,7 @@ v 8.11.0 (unreleased)
   - Ensure file editing in UI does not overwrite commited changes without warning user
   - Eliminate unneeded calls to Repository#blob_at when listing commits with no path
   - Update gitlab_git gem to 10.4.7
+  - Simplify SQL queries of marking a todo as done
 
 v 8.10.6
   - Upgrade Rails to 4.2.7.1 for security fixes. !5781

app/controllers/dashboard/todos_controller.rb

@@ -6,6 +6,8 @@ class Dashboard::TodosController < Dashboard::ApplicationController
   end
 
   def destroy
+    todo = Todo.new(id: params[:id])
+
     TodoService.new.mark_todos_as_done([todo], current_user)
 
     respond_to do |format|
@@ -27,10 +29,6 @@ class Dashboard::TodosController < Dashboard::ApplicationController
 
   private
 
-  def todo
-    @todo ||= find_todos.find(params[:id])
-  end
-
   def find_todos
     @todos ||= TodosFinder.new(current_user, params).execute
   end