Extend expiry of WebApk.Uninstall.*

BUG=1142501

Change-Id: I42170e8cdb660ae35275ea688b0c758de72b9fb6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2504269Reviewed-by: Glenn Hartmann <hartmanng@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Peter Kotwicz <pkotwicz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821846}

tools/metrics/histograms/histograms_xml/web_apk/histograms.xml

@@ -241,7 +241,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram base="true" name="WebApk.Uninstall" enum="BooleanHit"
-    expires_after="2020-12-06">
+    expires_after="2021-06-06">
   <owner>hartmanng@chromium.org</owner>
   <owner>
     src/chrome/android/java/src/org/chromium/chrome/browser/webapps/OWNERS