Update expiry date histograms

Bug: 1149451, 1149504
Change-Id: Ic24dcb714db843aae17aafd6ba83a2c7a83d7ae1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2543522Reviewed-by: Tony Yeoman <tby@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828054}

tools/metrics/histograms/histograms_xml/apps/histograms.xml

@@ -943,7 +943,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Apps.AppListResultLaunchIsEmptyQuery" enum="Boolean"
-    expires_after="2020-12-31">
+    expires_after="2021-11-15">
   <owner>thanhdng@chromium.org</owner>
   <owner>jiameng@chromium.org</owner>
   <summary>

tools/metrics/histograms/histograms_xml/power/histograms.xml

@@ -905,7 +905,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Power.SmartCharging.Messages" enum="SmartChargingMessages"
-    expires_after="2020-12-31">
+    expires_after="2021-11-15">
   <owner>thanhdng@chromium.org</owner>
   <owner>jiameng@chromium.org</owner>
   <summary>Type of messages that are reported by smart charging.</summary>