Update Note.java to match Anki 2.0.23.

Update Note.java to match Anki 2.0.23.

This is the first of many pull requests to come that will gradually update our version of libanki. I will send pull a pull request for each file that I do. The commit messages will also note which changes we are porting over.

During this exercise, I will be reviewing the existing code for errors (line-by-line!) and reformatting it according to our own style guidelines and to be as similar to upstream as possible (within reason). This includes anything from variable names to the order in which methods appear in the file. I want to make it as simple as possible to compare both versions side-by-side to find any discrepancies and to copy changes over in the future.