Bug 1488958 - Extend the telemetry.persistence_timer_hit_count. r=janerik

GeckoView is a bit more widespread now, but we still have no data
about how often the persistence timer is hit. Extending the lifetime
of this probe will allow us to have more data to reason about the
root cause of this.

Differential Revision: https://phabricator.services.mozilla.com/D5405

--HG--
extra : moz-landing-system : lando

toolkit/components/telemetry/Scalars.yaml

@@ -1525,7 +1525,7 @@ telemetry:
     description: >
       How many times the GeckoView Telemetry persistence timer was hit during
       the current subsession.
-    expires: "65"
+    expires: "70"
     kind: uint
     notification_emails:
       - telemetry-client-dev@mozilla.com