Remove CreateWebKitBuildDirectory step to fix Chromium Windows Perf bot

Remove CreateWebKitBuildDirectory step to fix Chromium Windows Perf bot
https://bugs.webkit.org/show_bug.cgi?id=84068

Reviewed by Eric Seidel.

Remove CreateWebKitBuildDirectory from master.cfg since download-built-product
automatically creates the build directory if needed.

* BuildSlaveSupport/build.webkit.org-config/master.cfg:
(DownloadAndPerfTestFactory.__init__):
(DownloadAndPerfTestWebKit2Factory.__init__):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114353 268f45cc-cd09-0410-ab3c-d52691b4dbfc