Update Get-TagsDocumentation.ps1 to update readme

scripts/Get-TagsDocumentation.ps1

@@ -1,6 +1,6 @@
 param(
     [string]$Branch='master',
-    [string]$ImageBuilderImageName='microsoft/dotnet-buildtools-prereqs:image-builder-jessie-20171031123612',
+    [string]$ImageBuilderImageName='microsoft/dotnet-buildtools-prereqs:image-builder-jessie-20171122115946',
     [string]$RepoName
 )
 
@@ -27,4 +27,4 @@ if ([String]::IsNullOrWhiteSpace($RepoName))
     -v "${repoRoot}:/repo" `
     -w /repo `
     $ImageBuilderImageName `
-    generateTagsReadme "https://github.com/dotnet/${RepoName}/blob/${Branch}"
+    generateTagsReadme --update-readme "https://github.com/dotnet/${RepoName}/blob/${Branch}"