WordPress/wp-includes/blocks/read-more/style.css

.wp-block-read-more{
  display:block;
  width:-moz-fit-content;
  width:fit-content;
}
.wp-block-read-more:not([style*=text-decoration]),.wp-block-read-more:not([style*=text-decoration]):active,.wp-block-read-more:not([style*=text-decoration]):focus{
  text-decoration:none;
}