fix celeborn metrics configuration doc

docs/configuration/metrics.md

@@ -31,6 +31,7 @@ license: |
 | celeborn.metrics.master.prometheus.port | 9098 | Master's Prometheus port. | 0.3.0 | 
 | celeborn.metrics.sample.rate | 1.0 | It controls if Celeborn collect timer metrics for some operations. Its value should be in [0.0, 1.0]. | 0.2.0 | 
 | celeborn.metrics.timer.slidingWindow.size | 4096 | The sliding window size of timer metric. | 0.2.0 | 
+| celeborn.metrics.worker.pauseSpentTime.forceAppend.threshold | 10 | Force append worker pause spent time even if worker still in pause serving state.Help user can find worker pause spent time increase, when worker always been pause state. |  | 
 | celeborn.metrics.worker.prometheus.host | <localhost> | Worker's Prometheus host. | 0.3.0 | 
 | celeborn.metrics.worker.prometheus.port | 9096 | Worker's Prometheus port. | 0.3.0 | 
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