Fix Az.SingaIR Syntax Errors (#17801)

Author: v-yuzhichen

src/SignalR/SignalR/help/New-AzWebPubSub.md

@@ -52,7 +52,7 @@ Name                Location      SkuName
 ----                --------      -------
 psdemo-wps          eastus        Standard_S1
 
-$wps | format-list
+$wps | Format-List
 
 DisableAadAuth               : False
 DisableLocalAuth             : False

src/SignalR/SignalR/help/Test-AzSignalRName.md

@@ -33,7 +33,7 @@ False
 
 ### Check an unexisted name.
 ```powershell
-Test-AzSignalR unexistedsignalr eastus
+Test-AzSignalRName -Name unexistedsignalr -Location eastus
 ```
 
 ```output

src/SignalR/SignalR/help/Update-AzWebPubSub.md

@@ -52,7 +52,7 @@ Name       Location SkuName
 ----       -------- -------
 psdemo-wps eastus   Standard_S1
 
-$wps | format-list
+$wps | Format-List
 
 DisableAadAuth               : False
 DisableLocalAuth             : False
@@ -72,7 +72,7 @@ ResourceName = 'psdemo-wps'
 SubscriptionId = $(Get-AzContext).Subscription.Id }
 $identity | Update-AzWebPubSub -EnableTlsClientCert
 
-$wps | format-list
+$wps | Format-List
 ```
 
 ```output