Extend OptimizationGuide histograms.

Bug: 1160820, 1160821, 1160822
Change-Id: Iaa846223faf3201598625d93299a3d93bb9796c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2642753
Commit-Queue: Michael Crouse <mcrouse@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Auto-Submit: Michael Crouse <mcrouse@chromium.org>
Reviewed-by: Sophie Chang <sophiechang@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845797}

tools/metrics/histograms/histograms_xml/optimization/histograms.xml

@@ -45,7 +45,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="OptimizationGuide.ClearFetchedHints.StoreAvailable"
-    units="BooleanAvailable" expires_after="2021-01-31">
+    units="BooleanAvailable" expires_after="M92">
   <owner>mcrouse@chromium.org</owner>
   <owner>sophiechang@chromium.org</owner>
   <summary>
@@ -157,7 +157,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="OptimizationGuide.HintsFetcher.GetHintsRequest.UrlCount"
-    units="total url count" expires_after="2021-01-31">
+    units="total url count" expires_after="M92">
   <owner>mcrouse@chromium.org</owner>
   <owner>sophiechang@chromium.org</owner>
   <summary>
@@ -284,7 +284,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram
     name="OptimizationGuide.PredictionManager.HasHostModelFeaturesForHost"
-    enum="Boolean" expires_after="2021-01-31">
+    enum="Boolean" expires_after="M92">
   <owner>mcrouse@chromium.org</owner>
   <owner>sophiechang@chromium.org</owner>
   <summary>