[Get-AzMetric.md]fix: don't worked example 4 (Azure#24653)

* Update Get-AzMetric.md

fix: don't worked example 4

* Update Get-AzMetric.md

src/Monitor/Monitor/help/Get-AzMetric.md

@@ -173,7 +173,7 @@ This command gets detailed output for the Requests metric.
 
 ### Example 4: Get summarized output for a specified metric with specified dimension filter
 ```powershell
-$dimFilter = @((New-AzMetricFilter -Dimension City -Operator eq -Value "Seattle","Toronto"), (New-AzMetricFilter -Dimension AuthenticationType -Operator eq -Value User))
+$dimFilter = "$(New-AzMetricFilter -Dimension City -Operator eq -Value "Seattle","Toronto") and $(New-AzMetricFilter -Dimension AuthenticationType -Operator eq -Value User)"
 
 Get-AzMetric -ResourceId <resourceId> -MetricName PageViews -TimeGrain 00:05:00 -MetricFilter $dimFilter -StartTime 2018-02-01T12:00:00Z -EndTime 2018-02-01T12:10:00Z -AggregationType Average
 ```