[attribution reporting] Extending Conversions.UniqueReportingOriginsP…

…erPage.* metrics

Bug: 1274662
Change-Id: I320175d9116f90de937a509becd24c394877bd5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3307074
Reviewed-by: John Delaney <johnidel@chromium.org>
Commit-Queue: Nan Lin <linnan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#946201}

tools/metrics/histograms/metadata/others/histograms.xml

@@ -4208,7 +4208,7 @@ chromium-metrics-reviews@google.com.
 </histogram>
 
 <histogram name="Conversions.UniqueReportingOriginsPerPage.Conversions"
-    units="origins" expires_after="2022-01-09">
+    units="origins" expires_after="M105">
   <owner>linnan@chromium.org</owner>
   <owner>johnidel@chromium.org</owner>
   <owner>measurement-api-dev+metrics@google.com</owner>
@@ -4221,7 +4221,7 @@ chromium-metrics-reviews@google.com.
 </histogram>
 
 <histogram name="Conversions.UniqueReportingOriginsPerPage.Impressions"
-    units="origins" expires_after="2022-01-09">
+    units="origins" expires_after="M105">
   <owner>linnan@chromium.org</owner>
   <owner>johnidel@chromium.org</owner>
   <owner>measurement-api-dev+metrics@google.com</owner>