Where is this inline CSS code [closed]

Question

The CSS code you’re seeing is added by core of WP when admin bar is showing.

The function that outputs it is called _admin_bar_bump_cb() and it’s called as hook on wp_head.

So how to get rid of it? Just remove this action from that hook:

function remove_admin_bar_bump() {
   remove_action( 'wp_head', '_admin_bar_bump_cb' );
}
add_action('get_header', 'remove_admin_bar_bump');

Then you can add it in your CSS and use body.admin-bar as context if you want to add some styles only if the admin bar is visible.