notifications - fix broken height compute

src/vs/workbench/browser/parts/notifications/media/notificationsList.css

@@ -18,7 +18,7 @@
 	opacity: 0;
 	position: absolute;
 	line-height: 22px;
-	height: calc(100% - 20px); /* 10px top and bottom */
+	margin: 10px 0; /* 10px top and bottom */
 	word-wrap: break-word; /* never overflow long words, but break to next line */
 }