enhance: remove flushed segmentInfo in WatchChannelRequest (#29526)

`WatchDmChannel` only need growing segment info, this PR removes fetch
segmentInfos when fill watch dml channel request.

---------

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

internal/querycoordv2/task/utils.go

@@ -198,7 +198,6 @@ func fillSubChannelRequest(
 ) error {
 	segmentIDs := typeutil.NewUniqueSet()
 	for _, vchannel := range req.GetInfos() {
-		segmentIDs.Insert(vchannel.GetFlushedSegmentIds()...)
 		segmentIDs.Insert(vchannel.GetUnflushedSegmentIds()...)
 	}