[Sync] Update expiry for Nigori keystore migration histograms

Due to not completed investigation about Nigori's not migrated to
keystore following histograms were extended until 2020-02-01:

Sync.EncryptEverythingWhenCryptographerNotReady
Sync.ShouldTriggerMigrationAfterMigration
Sync.IsNigoriMigratedAfterMigration
Sync.NigoriMigrationTrigger
Sync.NigoriMigrationAttemptedBeforeNotMigrated
Sync.NigoriMigrationReason

Bug: 944831, 995518, 995517, 995510, 995487
Change-Id: I89e834d31a1d41b37f1f070f537d15ae73ee0f18
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829351
Auto-Submit: Maksim Moskvitin <mmoskvitin@google.com>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702676}

tools/metrics/histograms/histograms.xml

@@ -142446,7 +142446,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="Sync.EncryptEverythingWhenCryptographerNotReady"
-    enum="Boolean" expires_after="2019-10-01">
+    enum="Boolean" expires_after="2020-02-01">
   <owner>mmoskvitin@google.com</owner>
   <owner>mastiz@chromium.org</owner>
   <owner>mamir@chromium.org</owner>
@@ -142893,7 +142893,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="Sync.IsNigoriMigratedAfterMigration" enum="Boolean"
-    expires_after="2019-10-01">
+    expires_after="2020-02-01">
   <owner>mmoskvitin@google.com</owner>
   <owner>mastiz@chromium.org</owner>
   <owner>mamir@chromium.org</owner>
@@ -143207,7 +143207,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="Sync.NigoriMigrationAttemptedBeforeNotMigrated" enum="Boolean"
-    expires_after="2019-10-01">
+    expires_after="2020-02-01">
   <owner>mmoskvitin@google.com</owner>
   <owner>mastiz@chromium.org</owner>
   <owner>mamir@chromium.org</owner>
@@ -143218,7 +143218,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="Sync.NigoriMigrationReason" enum="SyncNigoriMigrationReason"
-    expires_after="2019-10-01">
+    expires_after="2020-02-01">
   <owner>mmoskvitin@google.com</owner>
   <owner>mastiz@chromium.org</owner>
   <owner>mamir@chromium.org</owner>
@@ -143234,7 +143234,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="Sync.NigoriMigrationTrigger" enum="SyncNigoriMigrationTrigger"
-    expires_after="2019-10-01">
+    expires_after="2020-02-01">
   <owner>mmoskvitin@google.com</owner>
   <owner>mastiz@chromium.org</owner>
   <owner>mamir@chromium.org</owner>
@@ -144003,7 +144003,7 @@ should be kept until we use this API.  -->
 </histogram>
 
 <histogram name="Sync.ShouldTriggerMigrationAfterMigration" enum="Boolean"
-    expires_after="2019-10-01">
+    expires_after="2020-02-01">
   <owner>mmoskvitin@google.com</owner>
   <owner>mastiz@chromium.org</owner>
   <owner>mamir@chromium.org</owner>