Well the instructions does say you should inform IRCC of any errors with the Document. Depending on the error you could have held on to it until you receive the PR card but in this instance the child's height will be printed on the back of the card. So if you waited you will have to replace 2 documents instead of 1. I would suggest getting the child's COPR corrected as soon as possible.
By the way, when you submitted the application with her bio, how old was she and her height? If that information was correct (30cm) at the time of the application, then it is not an error. IRCC does not scale the height for correctness.
