Update Grant-CsExternalUserCommunicationPolicy.md

I see -Global parameter with PlatyPS but I cannot see it in another cmdlets... Also I have tried it in a demo tenant and I didn't see it being useful... I ran it alone and powershell ask me for PolicyName. Maybe we can set another policy as Global?

Author: dariomws

skype/skype-ps/skype/Grant-CsExternalUserCommunicationPolicy.md

@@ -15,7 +15,7 @@ Assigns an external user communication policy to one or more users or groups.
 ## SYNTAX
 
 ```
-Grant-CsExternalUserCommunicationPolicy [[-Identity] <UserIdParameter>] [[-PolicyName] <String>] [-Confirm] [-DomainController <Fqdn>] [-PassThru] [-Tenant <Guid>] [-WhatIf] [-AsJob] [<CommonParameters>]
+Grant-CsExternalUserCommunicationPolicy [[-Identity] <UserIdParameter>] [[-PolicyName] <String>] [-Confirm] [-DomainController <Fqdn>] [-PassThru] [-Global] [-Tenant <Guid>] [-WhatIf] [-AsJob] [<CommonParameters>]
 ```
 
 ## DESCRIPTION
@@ -185,6 +185,21 @@ Accept pipeline input: False
 Accept wildcard characters: False
 ```
 
+### -Global
+This parameter is reserved for internal Microsoft use.
+
+```yaml
+Type: SwitchParameter
+Parameter Sets: (All)
+Aliases:
+
+Required: False
+Position: Named
+Default value: None
+Accept pipeline input: False
+Accept wildcard characters: False
+```
+
 ### CommonParameters
 This cmdlet supports the common parameters: `-Debug, -ErrorAction, -ErrorVariable, -InformationAction, -InformationVariable, -OutVariable, -OutBuffer, -PipelineVariable, -Verbose, -WarningAction, and -WarningVariable. For more information, see about_CommonParameters (http://go.microsoft.com/fwlink/?LinkID=113216).`