[Autocomplete] Enable Autocomplete.Event collection

This histogram is enabled again to allow measuring the impact of coming
Autocomplete changes.

Bug: 1181759
Change-Id: I1c17c3676f22779a936de43d7d1fba7648530d1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2718109
Auto-Submit: Matthias Körber <koerber@google.com>
Commit-Queue: Matthias Körber <koerber@google.com>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#857795}

tools/metrics/histograms/histograms_xml/others/histograms.xml

@@ -1028,11 +1028,14 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Autocomplete.Events" enum="AutocompleteEvents"
-    expires_after="M85">
+    expires_after="M95">
   <owner>seblalancette@chromium.org</owner>
   <summary>
     Autocomplete events recorded when the user interacts with suggestions served
     from Autocomplete.
+
+    Note that this histogram was disabled after M85 and was only reenabled on
+    25.02.2021.
   </summary>
 </histogram>