i13n: Don't sample by pageview
Currently, the mw.eventLog.Schema class samples per pageview. However,
we expect that if a user is bucketed for a session, then all
EventLogging events logged during that session are in the sample.
Unlike Popups in I4f653bba, the RelatedArticles instrumentation does
rely on another mw.eventLog.Schema behavior: distinguishing between
static and dynamic data. This and the use of mw.eventLog.Schema could be
removed in a follow-on change.