Extend expiry of Enterprise.SystemFeaturesDisableList

As SystemFeaturesDisableList policy just launched, so
its UMA stats is still needed.

Bug: 1140030
Change-Id: I38191d0519554a215248e024acc8a86dd4f39402
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2487088Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Aya Elsayed <ayaelattar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819262}

tools/metrics/histograms/histograms_xml/enterprise/histograms.xml

@@ -1182,7 +1182,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Enterprise.SystemFeaturesDisableList" enum="SystemFeature"
-    expires_after="2020-12-01">
+    expires_after="2021-06-01">
   <owner>ayaelattar@chromium.org</owner>
   <owner>poromov@chromium.org</owner>
   <summary>