thrift: add missing cassert include for assert.
thrift: add missing cassert include for assert.

Reviewed By: strager

Differential Revision: D15339047

fbshipit-source-id: fa20210223f8af521013468df03589635dd31482

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift