I believe the following sets of CSS should do the trick with a few caveats.

The following code will resolve the issue across your entire site for that particular block type. I don’t really see a downside to this, but if you see something break on another page, you might try one of the other examples I am providing.

@media (max-width: 600px) {
	.wp-block-media-text {
		display: block;
	}
}

The following two sets are a little more focused in their target. This next bit of code targets that particular block, but only on blog posts.

@media (max-width: 600px) {
	.single-post .wp-block-media-text {
		display: block;
	}
}

This last one only targets the specific page you linked.

@media (max-width: 600px) {
	.postid-9267 .wp-block-media-text {
		display: block;
	}
}