Fix site logo preview image size with long filenames (#50242)

* Fix site logo preview image size with long filenames

* hardcode width value

Author: ntsekouras

packages/block-library/src/site-logo/editor.scss

@@ -138,7 +138,8 @@
 	}
 
 	img {
-		width: $grid-unit-50 * 0.5;
+		width: 20px;
+		min-width: 20px;
 		aspect-ratio: 1;
 		box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.2);
 		border-radius: 50% !important;