Encoder side bug fix: the encoder speed up in palette (which bypass INTRA mode...

Encoder side bug fix: the encoder speed up in palette (which bypass INTRA mode check in inter slice if palette mode is better than INTER mode)
shouldn't be applied on 4x4 blocks since JVET-N0266 disabled INTER mode in 4x4 blocks.
Without the fix, intra mode will always be skipped in 4x4 blocks in inter slice if IBC is disabled in SPS.