[Paper 1.21.10] CustomBlockData is not abstract and does not override abstract method getSize() in PersistentDataContainerView

[globau]

Compilation error after upgrading to Paper 1.21.10:

…/com/jeff_media/customblockdata/CustomBlockData.java:57: error: CustomBlockData is not abstract and does not override abstract method getSize() in PersistentDataContainerView
public class CustomBlockData implements PersistentDataContainer {

This was added by https://github.com/PaperMC/Paper/pull/13157.