Including backup item .cs file which was missed in the merge conflict resolution in the previous commit

Author: dragonfly91

src/ResourceManager/RecoveryServices.Backup/Commands.RecoveryServices.Backup.Cmdlets.csproj

@@ -82,6 +82,7 @@
     <Compile Include="Cmdlets\Container\GetAzureRmRecoveryServicesContainer.cs" />
     <Compile Include="Cmdlets\Container\UnregisterAzureRmBackupManagementServer.cs" />
     <Compile Include="Cmdlets\Container\UnregisterAzureRmRecoveryServicesBackupContainer.cs" />
+    <Compile Include="Cmdlets\Item\BackupAzureRmRecoveryServicesItem.cs" />
     <Compile Include="Cmdlets\Item\EnableAzureRmRecoveryServicesProtection.cs" />
     <Compile Include="Cmdlets\Item\GetAzureRmRecoveryServicesItem.cs" />
     <Compile Include="Cmdlets\Jobs\GetAzureRmRecoveryServicesJob.cs" />