Remove unnecessary namespaced resource

app/controllers/admin/members_controller.rb

+class Admin::MembersController < Admin::ApplicationController
+  def destroy
+    user = User.find_by_username(params[:id])
+    project = Project.find_with_namespace(params[:project_id])
+    project.users_projects.where(user_id: user).first.destroy
+
+    redirect_to :back
+  end
+end

app/controllers/admin/projects/application_controller.rb

-# Provides a base class for Admin controllers to subclass
-#
-# Automatically sets the layout and ensures an administrator is logged in
-class Admin::Projects::ApplicationController < Admin::ApplicationController
-
-  protected
-
-  def project
-    @project ||= Project.find_with_namespace(params[:project_id])
-  end
-end

app/controllers/admin/projects/members_controller.rb

-class Admin::Projects::MembersController < Admin::Projects::ApplicationController
-  def destroy
-    team_member_relation.destroy
-
-    redirect_to :back
-  end
-
-  private
-
-  def team_member
-    @member ||= project.users.find_by_username(params[:id])
-  end
-
-  def team_member_relation
-    team_member.users_projects.find_by_project_id(project)
-  end
-end

config/routes.rb

@@ -88,10 +88,8 @@ Gitlab::Application.routes.draw do
     resource :background_jobs, controller: 'background_jobs', only: [:show]
 
     resources :projects, constraints: { id: /[a-zA-Z.\/0-9_\-]+/ }, only: [:index, :show] do
-      scope module: :projects, constraints: { id: /[a-zA-Z.\/0-9_\-]+/ } do
       resources :members, only: [:destroy]
     end
-    end
 
     root to: "dashboard#index"
   end