[Zucchini] upload zucchini.exe to unsigned staging on win official

Whitelist zucchini.exe for upload to unsigned staging for experimental
integration with diff infra.

This is a followup to:
https://chromium-review.googlesource.com/c/chromium/src/937396

Bug: 729154
Change-Id: Id0da2fb5aca31782ef11e81dc47abf7706df2b52
Reviewed-on: https://chromium-review.googlesource.com/939665
Commit-Queue: Calder Kitagawa <ckitagawa@google.com>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Michael Moss <mmoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539550}

chrome/tools/build/win/FILES.cfg

@@ -656,6 +656,12 @@ FILES = [
     'buildtype': ['official'],
     'archive': 'courgette64.exe',
   },
+  {
+    'filename': 'zucchini.exe',
+    'buildtype': ['official'],
+    'optional': ['official'],
+    'archive': 'zucchini.exe',
+  },
   {
     'filename': 'chrome.dll.pdb',
     'buildtype': ['dev', 'official'],