3.1.5 — Remove usage of custom GridFieldOrderableRow class
Explicitly requires version ^3.2.3 of the symbiote/silverstripe-gridfieldextensions module, which includes a fix that supports GridFieldOrderableRow for polymorphic many_many_through relation. This enables this module to swap back to use GridFieldOrderableRow class from the original module and drop the work-around class GridFieldOrderableRow extended from the origin.