For pages:

//hide content editor in dashboard page
add_action('init', 'remove_content_editor');

function remove_content_editor() {
    remove_post_type_support( 'page', 'editor' );
}

For posts:

//hide content editor in dashboard page
add_action('init', 'remove_content_editor');

function remove_content_editor() {
    remove_post_type_support( 'post', 'editor' );
}