Extend Sync.CustomEncryption histogram by one year

Bug: 1152039
Change-Id: I1baedf226b8848951ac50f5370aa8b80feb06b74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567165
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833519}

tools/metrics/histograms/histograms_xml/sync/histograms.xml

@@ -286,7 +286,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Sync.CustomEncryption" enum="SyncCustomEncryptionEvent"
-    expires_after="2021-01-03">
+    expires_after="2022-01-03">
   <owner>mastiz@chromium.org</owner>
   <owner>treib@chromium.org</owner>
   <summary>