Added argument to -Lock parameter

Need to talk to @mwrock about this, as I don't think this should be required, however, when I just tried it, I got this:

Set-TaskbarOptions : Missing an argument for parameter 'Lock'. Specify a
parameter of type 'System.Object' and try again.
At line:1 char:32
+ Set-TaskbarOptions -Size Small -Lock -Dock Left
+                                ~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Set-TaskbarOptions], Param
   eterBindingException
    + FullyQualifiedErrorId : MissingArgument,Set-TaskbarOptions

Until I added it