Extend experation date for Tabs.SadTab.Reload.Event and Tabs.SadTab.Feedback.Event

These histograms are useful for monitoring user-visible renderer crashes
on iOS. Might be useful on other platforms as well.

Bug: 1089568, 1089567
Change-Id: I40d38b162fccc356d3373f2e16d491e6bf29725f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615719
Auto-Submit: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841235}

tools/metrics/histograms/histograms_xml/tab/histograms.xml

@@ -1505,7 +1505,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Tabs.SadTab.Feedback.Event" enum="SadTabEvent"
-    expires_after="M85">
+    expires_after="2021-06-01">
   <owner>sonnyrao@chromium.org</owner>
   <owner>jamescook@chromium.org</owner>
   <summary>
@@ -1599,7 +1599,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Tabs.SadTab.Reload.Event" enum="SadTabEvent"
-    expires_after="M85">
+    expires_after="2021-06-01">
   <owner>sonnyrao@chromium.org</owner>
   <owner>jamescook@chromium.org</owner>
   <summary>