Featured Image Block: Reduce CSS specificity (#64463)

Co-authored-by: dsas <dsas@git.wordpress.org>
Co-authored-by: aaronrobertshaw <aaronrobertshaw@git.wordpress.org>
Co-authored-by: talldan <talldanwp@git.wordpress.org>
Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: andrewserong <andrewserong@git.wordpress.org>

packages/block-library/src/post-featured-image/style.scss

@@ -5,7 +5,7 @@
 		display: block;
 		height: 100%;
 	}
-	img {
+	:where(img) {
 		max-width: 100%;
 		width: 100%;
 		height: auto;