Editing admin bar

I’ve been using a piece of code in functions.php of my theme but it keeps disappearing:

function remove_comments_column( $columns ) {
unset($columns['comments']);
unset($columns['tags']);
return $columns;
}

function remove_column_init() {
add_filter( 'manage_posts_columns' , 'remove_comments_column' );

}
add_action( 'admin_init' , 'remove_column_init' );

I have one plugin, yoast seo which adds an element to the admin that I can’t seem to remove. I thought this was achieved from inside the plugin but it doesn’t go away.

I will save this and come back to find it has been deleted. What is happening?