Update Get-AzSynapseTriggerRun.md (#15231)

The current example throws an errors

```
Cannot bind parameter 'RunStartedAfter'. Cannot convert value "[DateTimeOffset]2018-09-01T21:00" to 
type "System.DateTimeOffset". Error: "String was not recognized as a valid DateTime."
```

src/Synapse/Synapse/help/Get-AzSynapseTriggerRun.md

@@ -31,15 +31,15 @@ The **Get-AzSynapseTriggerRun** command returns detailed information about trigg
 
 ### Example 1
 ```powershell
-PS C:\> Get-AzSynapseTriggerRun -WorkspaceName ContosoWorkspace -Name ContosoTrigger -RunStartedAfter [DateTimeOffset]"2018-09-01T21:00" -RunStartedBefore [DateTimeOffset]"2019-09-01T21:00"
+PS C:\> Get-AzSynapseTriggerRun -WorkspaceName ContosoWorkspace -Name ContosoTrigger -RunStartedAfter "2018-09-01T21:00" -RunStartedBefore "2019-09-01T21:00"
 ```
 
 This command shows information about runs for ContosoTrigger in the workspace ContosoWorkspace that started between "2018-09-01T21:00" and "2019-09-01T21:00".
 
 ### Example 2
 ```powershell
 PS C:\> $ws = Get-AzSynapseWorkspace -Name ContosoWorkspace
-PS C:\> $ws | Get-AzSynapseTriggerRun -Name ContosoTrigger -RunStartedAfter [DateTimeOffset]"2018-09-01T21:00" -RunStartedBefore [DateTimeOffset]"2019-09-01T21:00"
+PS C:\> $ws | Get-AzSynapseTriggerRun -Name ContosoTrigger -RunStartedAfter "2018-09-01T21:00" -RunStartedBefore "2019-09-01T21:00"
 ```
 
 This command shows information about runs for ContosoTrigger in the workspace ContosoWorkspace that started between "2018-09-01T21:00" and "2019-09-01T21:00" through pipeline.