[Realbox] Extend expiration date for realbox latency metric

This is a key realbox performance metric.

Fixed: 1066045
Change-Id: I8a72c820c888f8235b3e5d4d73c2d1e1feb23f85
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2632266
Auto-Submit: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845235}

tools/metrics/histograms/histograms_xml/new_tab_page/histograms.xml

@@ -1059,7 +1059,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="NewTabPage.Realbox.CharTypedToRepaintLatency.ToPaint"
-    units="ms" expires_after="M83">
+    units="ms" expires_after="2022-01-01">
   <owner>mahmadi@chromium.org</owner>
   <owner>tommycli@chromium.org</owner>
   <owner>chrome-desktop-ntp@google.com</owner>