[4.0] (#34910) Updating or uninstalling one library no longer removes…

… another when both belong to same vendor.

### Summary of Changes
Check if there are any other children before removing vendor folder.

### Testing instructions
As described in #34910

libraries/src/Installer/Adapter/LibraryAdapter.php

@@ -309,8 +309,12 @@ protected function removeExtensionFiles()
 		// Delete empty vendor folders
 		if (2 === \count($elementParts))
 		{
-			Folder::delete(JPATH_MANIFESTS . '/libraries/' . $elementParts[0]);
-			Folder::delete(JPATH_PLATFORM . '/' . $elementParts[0]);
+			$folders = Folder::folders(JPATH_PLATFORM . '/' . $elementParts[0], '.', false, true, array(), array());
+			if (empty($folders))
+			{
+				Folder::delete(JPATH_MANIFESTS . '/libraries/' . $elementParts[0]);
+				Folder::delete(JPATH_PLATFORM . '/' . $elementParts[0]);
+			}
 		}
 	}