Update another AnchorElementMetrics expiry

This didn't have the fixit label initially, so I happened to miss
updating the expiry.

Bug: 1061962
Change-Id: Ib4b9311dccf6fa489e2a2a9180d38d7b4328a009
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2163068
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Auto-Submit: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761967}

tools/metrics/histograms/histograms.xml

@@ -1925,7 +1925,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="AnchorElementMetrics.Visible.NumberOfAnchorElementsAfterMerge"
-    units="count" expires_after="2020-04-26">
+    units="count" expires_after="2021-04-26">
   <owner>chelu@chromium.org</owner>
   <owner>tbansal@chromium.org</owner>
   <summary>