[Histograms] Extend expiry date of Signin.Sync* histograms

As we're changing settings screen for MOBILE_IDENTITY_CONSISTENCY, it
makes sense to keep these histograms related to settings for some more
time.

Bug: 1153770
Change-Id: I8b2d5c5db4007405322c7703393df9f4814faf19
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2571364Reviewed-by: Tanmoy Mollik <triploblastic@chromium.org>
Reviewed-by: Alex Ilin <alexilin@chromium.org>
Commit-Queue: Tanmoy Mollik <triploblastic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834426}

tools/metrics/histograms/histograms_xml/signin/histograms.xml

@@ -1097,7 +1097,7 @@ kept as long as profile signout is possible -->
 </histogram>
 
 <histogram base="true" name="Signin.SyncErrorInfoBar"
-    enum="SyncErrorInfoBarAction" expires_after="M89">
+    enum="SyncErrorInfoBarAction" expires_after="2021-06-01">
 <!-- Name completed by histogram_suffixes name="SyncErrorInfoBarType" -->
 
   <owner>triploblastic@chromium.org</owner>
@@ -1109,7 +1109,7 @@ kept as long as profile signout is possible -->
 </histogram>
 
 <histogram name="Signin.SyncFirstSetupCompleteSource"
-    enum="SyncFirstSetupCompleteSource" expires_after="M89">
+    enum="SyncFirstSetupCompleteSource" expires_after="2021-06-01">
   <owner>triploblastic@chromium.org</owner>
   <owner>bsazonov@chromium.org</owner>
   <summary>Tracks where FirstSetupComplete bit is set from.</summary>