private void fileRemoved(String filename) {
		String fileID = null;
		GhidraFileData fileData = fileDataCache.remove(filename);
		if (fileData != null) {
			fileID = fileData.getFileID();
			fileData.dispose();
		}
		if (visited) {
			listener.domainFileRemoved(getDomainFolder(), filename, fileID);
		}
	}
Refresh set of sub-folder names and identify added/removed folders.
@param recursive recurse into visited subfolders if true
@param monitor recursion task monitor - break from recursion if cancelled
@throws IOException if an IO error occurs during the refresh
Ghidra/Framework/Project/src/main/java/ghidra/framework/data/GhidraFolderData.java