mw.Target: Add class "mw-ve-editNotice" to edit notices

Follows-up I260059802379 which removed got rid of
the "ve-init-mw-viewPageTarget-toolbar-editNotices-notice" class
from notices and didn't add something generic in its place.

(There is "ve-ui-mwNoticesPopupTool-item" but that's more an
internal class we don't want gadgets and wiki stylesheets to
rely on.)

Bug: 43013
Change-Id: I8e1e383c2cb3199fe78f45f4feaa24a44126cf0b