Setting CommandExp ExcludeFilter to be empty array (PowerShell#1738)

Fixes PowerShell#1737

Author: adilio

package.json

@@ -504,7 +504,7 @@
         },
         "powershell.sideBar.CommandExplorerExcludeFilter": {
           "type":"array",
-          "default":"",
+          "default":[],
           "description": "Specify array of Modules to exclude from Command Explorer listing."
         },
         "powershell.powerShellExePath": {