Overriding comment form defaults in child theme

I am modifying a child theme, and the theme has a function declaration like this:

function academica_comment_form_defaults( $args ) {
        $args['title_reply'] = __( 'Post a Comment', 'academica' );
        return $args;
}
add_filter( 'comment_form_defaults', 'academica_comment_form_defaults' );

I would like to override this behavior in my child theme so that I can put my own text instead of “Post a Comment”.
Is there an easy way to do this? Would I create a custom function in my child theme’s functions.php file?

Thanks so much…