Replace -is:draft

That flag has been retired by Gerrit a long time ago and was
replaced with -is:private and -is:wip for different aspects of
what a draft change has been previously.

Change-Id: I47db8d9e66864525f35fa45f2136fd2c711b40e9
Reviewed-on: https://review.coreboot.org/c/flashrom/+/67280
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Nico Huber <nico.h@gmx.de>

project.config

@@ -71,4 +71,4 @@
 [notify "flashrom-gerrit"]
 	header = to
 	email = flashrom-gerrit@flashrom.org
-	filter = -is:draft
+	filter = -is:private -is:wip