Specify correct Constants message for UpdateAzCosmosDBAccountRegion InputObject parameter

[plzm]

https://github.com/Azure/azure-powershell/blob/master/src/CosmosDB/CosmosDB/CosmosDBAccount/UpdateAzCosmosDBAccountRegion.cs#L49

Currently the HelpMessage attrib is Constants.ResourceIdHelpMessage. Should be Constants.AccountObjectHelpMessage

[MehaKaushik]

In PR #11388