Use Emergency Force Push to control skipping validation.

Motivation:
Currently All-Projects exempts infra team members from the validation.
This is not ideal.
I am making this change in Public-Projects rather than All-Projects
because All-Projects contains the actual black-list of banned words, so
edits to it would be very painful if we don't let the infra team bypass
the check on All-Projects.
This seems logically very similar to the current usage of Emergency
Force Push.

Change-Id: Ib605577d80828db512cc937a60563b87323d8ccc
diff --git a/project.config b/project.config
index 89ee452..80c12fe 100644
--- a/project.config
+++ b/project.config
@@ -5,3 +5,5 @@
 	read = group Registered Users
 [submit]
 	action = rebase if necessary
+[plugin "uploadvalidator"]
+	skipGroup = Emergency Force Push