kv: remove clock update on BatchResponse

Before this change, we were updating the local clock with each BatchResponse's
WriteTimestamp. This was meant to handle cases where the batch request timestamp
was forwarded during evaluation.

This was unnecessary for two reasons. The first is that BatchRequest can lead
the local HLC clock (explored in #72121 and #72278) as long as any clock reading
information in the values reflects the state of the HLC clock (synthetic bit
today, "local timestamp" tomorrow). The second is that even if this first reason
was not the case, the BatchRequest will only ever be bumped one logical tick
above any existing value in the range, so as long as the existing values in the
range followed the rule of trailing the leaseholders HLC (NB: they don't), all
new writes would too.

pkg/kv/kvserver/store_send.go

@@ -108,23 +108,6 @@ func (s *Store) Send(
 				if br.Txn == nil {
 					br.Txn = ba.Txn
 				}
-				// Update our clock with the outgoing response txn timestamp
-				// (if timestamp has been forwarded).
-				if ba.Timestamp.Less(br.Txn.WriteTimestamp) {
-					if clockTS, ok := br.Txn.WriteTimestamp.TryToClockTimestamp(); ok {
-						s.cfg.Clock.Update(clockTS)
-					}
-				}
-			}
-		} else {
-			if pErr == nil {
-				// Update our clock with the outgoing response timestamp.
-				// (if timestamp has been forwarded).
-				if ba.Timestamp.Less(br.Timestamp) {
-					if clockTS, ok := br.Timestamp.TryToClockTimestamp(); ok {
-						s.cfg.Clock.Update(clockTS)
-					}
-				}
 			}
 		}