OrcRawRecordMerger collapseEvents mode should not produce delete events

it made sense before HIVE-17089 where we had multiple versions of the same row and this mode produce the latest one.
Now outputting delete events is only need for compaction and VectorizedOrcAcidRowBatchReader. The latter only reads delete_delta and OrcInputFormat skips all delete events from OrcRawRecordMerger