How do I change the ‘… Read more’ text

In your theme’s functions.php file, add similar code as follows.

add_filter( 'testimonials_widget_premium_more_ellipsis', function() { return ' '; } );
add_filter( 'testimonials_widget_premium_more_text', function() { return ' Continue reading →'; } );

or

function my_testimonials_widget_premium_more_ellipsis() { return ' Continue reading →'; }
add_filter( 'testimonials_widget_premium_more_ellipsis', 'my_testimonials_widget_premium_more_ellipsis' );
function my_content_more() { return ' '; }
add_filter( 'testimonials_widget_premium_more_text', 'my_content_more' );