ovsdb: Update NEWS for fast-resync feature.

This patch updates text in NEWS committed by 5832e6a, so that it is
easier to understand for end users.

Signed-off-by: Han Zhou <hzhou8@ebay.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

NEWS

@@ -17,11 +17,11 @@ Post-v2.11.0
        conntrack fragmentation support.
      * New "ovs-appctl dpctl/ipf-get-status" command for userspace datapath
        conntrack fragmentation support.
-    - OVSDB:
-     * Support new monitoring method "monitor_cond_since" for fast data
-       resync upon server restart or fail-over. The feature is available
-       for C-IDL clients with clustered mode servers. See section 4.1.15
-       of ovsdb-server(7) for more details.
+   - OVSDB:
+     * OVSDB clients can now resynchronize with clustered servers much more
+       quickly after a brief disconnection, saving bandwidth and CPU time.
+       See section 4.1.15 of ovsdb-server(7) for details of related OVSDB
+       protocol extension.
 
 v2.11.0 - 19 Feb 2019
 ---------------------