Still there on my setup. Did you also upgrade the vassal version? If so, your extensions directory may have changed - check preferences-> extensions and make sure that TerrainChart1.2.1 is in the required directory. If the directory is not set in preferences, set it to where you have TerrainChart1.2.1.
If you deleted the previous version of VASSAL (which VASSAL does as the default setting when installing a new version) that might have taken your extensions with it.