Windows: Auto-confirm chocolatey upgrades

Chocolatey has a new version for the first time in a long while, so this
code path was never exercised before.

Fixes: #8

minicoin/roles/windows-tools/provision.ps1

@@ -44,7 +44,7 @@ if (!(Test-Path $ChocoInstallPath)) {
 } else {
     write-host "Upgrade Chocolatey . . . "
     cd $ChocoInstallPath
-    .\choco upgrade chocolatey
+    .\choco upgrade --confirm chocolatey
     write-host "END Upgrade Chocolatey!"
 }