config: fix trace-region-flow displayed incorrectly (#7993) (#8064)

close #7917

Signed-off-by: Ryan Leung <rleungx@gmail.com>

Co-authored-by: Ryan Leung <rleungx@gmail.com>

server/config/config.go

@@ -199,7 +199,6 @@ const (
 	defaultLeaderPriorityCheckInterval = time.Minute
 
 	defaultUseRegionStorage  = true
-	defaultTraceRegionFlow   = true
 	defaultFlowRoundByDigit  = 3 // KB
 	maxTraceFlowRoundByDigit = 5 // 0.1 MB
 	defaultMaxResetTSGap     = 24 * time.Hour
@@ -1102,9 +1101,6 @@ func (c *PDServerConfig) adjust(meta *configutil.ConfigMetaData) error {
 	if !meta.IsDefined("dashboard-address") {
 		c.DashboardAddress = defaultDashboardAddress
 	}
-	if !meta.IsDefined("trace-region-flow") {
-		c.TraceRegionFlow = defaultTraceRegionFlow
-	}
 	if !meta.IsDefined("flow-round-by-digit") {
 		configutil.AdjustInt(&c.FlowRoundByDigit, defaultFlowRoundByDigit)
 	}