Extend VoiceInteraction.* histograms to M81.

BUG=975753

Change-Id: Ic2f7207594400613bb3b26ddcbd78df44947864c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1707824Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680042}

tools/metrics/histograms/histograms.xml

@@ -145451,7 +145451,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="VoiceInteraction.FailureEventSource"
-    enum="VoiceInteractionEventSource" expires_after="M77">
+    enum="VoiceInteractionEventSource" expires_after="M81">
   <owner>tedchoc@chromium.org</owner>
   <owner>yusufo@chromium.org</owner>
   <summary>
@@ -145500,7 +145500,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="VoiceInteraction.VoiceResultConfidenceValue" units="%"
-    expires_after="M77">
+    expires_after="M81">
   <owner>tedchoc@chromium.org</owner>
   <owner>yusufo@chromium.org</owner>
   <summary>