It is simple just some uninstalling an removing some files.
First uninstall following package in package manage console:
PM> uninstall-Package Microsoft.Owin.Security.Facebook
PM> uninstall-Package Microsoft.Owin.Security.Google
PM> uninstall-Package Microsoft.Owin.Security.MicrosoftAccount
PM> uninstall-Package Microsoft.Owin.Security.Twitter
PM> uninstall-Package Microsoft.Owin.Host.SystemWeb
PM> uninstall-Package Microsoft.AspNet.Identity.EntityFramework
PM> uninstall-Package Microsoft.AspNet.Identity.Owin
If everything goes right your project must clean up with following packeges:
Microsoft.AspNet.Identity.Core
Microsoft.AspNet.Identity.EntityFramework
Microsoft.AspNet.Identity.Owin
Microsoft.Owin
Microsoft.Owin.Host.SystemWeb
Microsoft.Owin.Security
Microsoft.Owin.Security.Cookies
Microsoft.Owin.Security.Facebook
Microsoft.Owin.Security.Google
Microsoft.Owin.Security.MicrosoftAccount
Microsoft.Owin.Security.OAuth
Microsoft.Owin.Security.Twitter
Owin
So if anyone still exist simply uninstall them also.
Now you could remove following files from your project:
App_Start\IdentityConfig.cs
App_Start\Startup.Auth.cs
Models\IdentityModels.cs
Startup.cs