When you delete a post, it merely gets put into the “trash” and retains its slug. When you created the “new” contact page, the slug “contact” was already in use by the original contact post that is in the trash.
Go into your posts on the dashboard and click on the “Trash” link near the top of the post listing. Once in the Trash area, permanently delete the original contact post.
You can now go back into the “new” contact post, edit the slug near the top of the post, and remove the extra -2 that was added to it. Click OK and save the post. It should now have the slug contact instead of contact-2