2491: Prevent URN map generation during indexing.

Refactored notification text formatting for clarity and consistency. This ensures users are properly informed to wait until indexing is complete before generating URN maps. Enhances user guidance and prevents unwanted actions during indexing.

Author: VitaliyBoyko

src/main/java/com/magento/idea/magento2plugin/project/RegenerateUrnMapListener.java

@@ -59,9 +59,9 @@ public void mouseClicked(final MouseEvent event) {
                     .getNotificationGroup("Magento Notifications")
                     .createNotification(
                             "URN map generation unavailable",
-                            "Indexing is in progress." +
-                                    " Please wait for it to complete" +
-                                    " before running URN mapping generation.",
+                            "Indexing is in progress."
+                                    + " Please wait for it to complete"
+                                    + " before running URN mapping generation.",
                             NotificationType.WARNING
                     )
                     .notify(project);