storage: fix incorrect listener on concurrent AddSST setting

Copy/paste mistake meant that the wrong setting was being used to trigger the re-read of the setting on-update.

Release note (bug fix): fix bug that prevented changes to kv.bulk_io_write.concurrent_addsstable_requests from taking effect.

Release justification: very small, low-risk fix for user-visible bug in existing code.

pkg/storage/store.go

@@ -897,7 +897,7 @@ func NewStore(
 	s.limiters.ConcurrentAddSSTableRequests = limit.MakeConcurrentRequestLimiter(
 		"addSSTableRequestLimiter", int(addSSTableRequestLimit.Get(&cfg.Settings.SV)),
 	)
-	importRequestsLimit.SetOnChange(&cfg.Settings.SV, func() {
+	addSSTableRequestLimit.SetOnChange(&cfg.Settings.SV, func() {
 		s.limiters.ConcurrentAddSSTableRequests.SetLimit(int(addSSTableRequestLimit.Get(&cfg.Settings.SV)))
 	})
 	s.limiters.ConcurrentRangefeedIters = limit.MakeConcurrentRequestLimiter(