I have tried to use code mentioned in dev note but it is not working, this is the snippet I have tried:

function set_fetchpriority_high_on_specific_image( $loading_attrs, $tag_name, $attr, $context ) {
    if ( 'img' === $tag_name ) {
        if (
            'the_content' === $context &&
            isset( $attr['src'] ) &&
            $attr['src'] === 'https://example.org/a-specific-image.jpg'
        ) {
            $loading_attrs['fetchpriority'] = 'high';
        } else {
            unset( $loading_attrs['fetchpriority'] );
        }
    }
    return $loading_attrs;
}
add_filter(
    'wp_get_loading_optimization_attributes',
    'set_fetchpriority_high_on_specific_image',
    10,
    4
);

I am not to add fetchpriority high by comparing the url of the image in WordPress using the hook.