Adding function to child theme’s function.php

You can’t recall the same function or PHP will throw an error. Make your own function and call the same action hook, but give it a priority of 1 which should overrule the parent theme function.

function custom_oblique_post_link_to_single() {
if ( ! get_theme_mod( 'read_more' ) ) :?>
<a href="https://wordpress.stackexchange.com/questions/282703/<?php the_permalink(); ?>">
<div class="read-more">
<?php echo apply_filters( 'oblique_post_read_more' ,
esc_html__( 'Continue Reading &hellip;','oblique' ) ); ?>
</div>
</a>
<?php
endif;
add_action( 'oblique_link_to_single','custom_oblique_post_link_to_single', 1 );