Switch static-special from copy to synchronize

According to notes in the Ansible documentation for the copy module,
it "does not scale to lots (>hundreds) of files." Several of the 5
sites currently relying on the publish/static-special playbook have
content numbering in the thousands of files. Other sites on the same
server instead rely on the publish/static playbook which already
uses synchronize instead of copy, so this should be entirely
compatible.

Change-Id: Iac85d906ae7c7a4666d7a5eeaa73b5a9f2ac7115

playbooks/publish/static-special.yaml

@@ -14,7 +14,7 @@
   gather_facts: False
   tasks:
     - name: Upload docs to static site
-      copy:
+      synchronize:
         src: "{{ zuul.executor.work_root }}/artifacts/"
         dest: "{{ fileserver.path }}/{{ static_target }}/"
       when: zuul_success | bool