2.16: Consolidate NoteDb migration in a single section under "Important Notes"

Also remove the duplicate statement about git client support.

Change-Id: I4c7d673ae906cfae68c7666af648c54e6d9531d5
diff --git a/pages/site/releases/2.16.md b/pages/site/releases/2.16.md
index 79cd7ef..11d634c 100644
--- a/pages/site/releases/2.16.md
+++ b/pages/site/releases/2.16.md
@@ -28,17 +28,30 @@
 
 ## Important Notes
 
+### Migration to NoteDb
+
 [NoteDb](https://gerrit-documentation.storage.googleapis.com/Documentation/2.16/note-db.html)
 is now required for accounts (since 2.15) and groups (since 2.16), and is the preferred storage for changes.
 
+In Gerrit 2.15:
+* Account data (with the exception of Group data) was moved to NoteDB ([release notes](https://www.gerritcodereview.com/2.15.html#notedb-for-accounts)).
+* Change data could be either moved to NoteDB ([migration process](https://gerrit-documentation.storage.googleapis.com/Documentation/2.15/note-db.html#migration)), or left in ReviewDB.
+
+In Gerrit 2.16:
+* Group data is always moved to NoteDB (it is migrated automatically during the upgrade process, when you run `gerrit.war init`).
+
 When upgrading to Gerrit v2.16, you are strongly advised to migrate fully (including changes) from ReviewDb to NoteDb.
 
+You should review the documentation on [NoteDb](https://gerrit-documentation.storage.googleapis.com/Documentation/2.16/note-db.html),
+including the information about the migration process:
+
+- [On-line migration](https://gerrit-review.googlesource.com/Documentation/note-db.html#online-migration)
+- [Off-line migration](https://gerrit-review.googlesource.com/Documentation/note-db.html#offline-migration)
+
 Although ReviewDb is still technically available on Gerrit v2.16, the upgrade to NoteDb is strongly recommended, although not enforced.
 
 Note that in the next version of Gerrit (v3.0), ReviewDb will not be available.
 
-Drop support for git clients older than 2.2.x.
-
 ### Schema Changes
 
 This release contains schema changes. To upgrade:
@@ -71,22 +84,6 @@
 offline. These will automatically be reindexed by the online reindexer after
 starting Gerrit.
 
-### Migration to NoteDb
-
-You should review the documentation on [NoteDb](https://gerrit-documentation.storage.googleapis.com/Documentation/2.16/note-db.html),
-including the information about the migration process:
-
-- [On-line migration](https://gerrit-review.googlesource.com/Documentation/note-db.html#online-migration)
-- [Off-line migration](https://gerrit-review.googlesource.com/Documentation/note-db.html#offline-migration)
-
-In Gerrit 2.15:
-* Account data (with the exception of Group data) was moved to NoteDB ([release notes](https://www.gerritcodereview.com/2.15.html#notedb-for-accounts)).
-* Change data could be either moved to NoteDB ([migration process](https://gerrit-documentation.storage.googleapis.com/Documentation/2.15/note-db.html#migration)), or left in ReviewDB.
-
-In Gerrit 2.16:
-* Group data is always moved to NoteDB (it is migrated automatically during the upgrade process, when you run `gerrit.war init`).
-
-
 ### Support for GWT UI is deprecated
 
 From 2.16 GWT UI is deprecated and will be removed in a future version.