Line buffer reduction for context modeling (CWG-F184) not applied for CDEF

As part of CWG-F184, the context modeling across superblock boundaries was removed for CDEF. However, the change is not reflected in the current version of the code.

Relevant code: https://gitlab.com/AOMediaCodec/avm/-/blob/main/av1/common/pred_common.c#L668-681