fix(ui5-illustrated-message): vertical alignment (#8566)

Recent DOT feature led to improper vertical alignment of Illustrated
Message's SVG when the IM is inside tall container.
Now we make sure both the text and the SVG container are vertically
centered in case of tall container.
Fixes: #8490

packages/fiori/src/themes/IllustratedMessage.css

@@ -17,6 +17,7 @@
     align-items: center;
     justify-content: center;
     height:inherit;
+    flex-basis: content;
 }
 
 .ui5-illustrated-message-illustration {