docs: fix syntax highlighting of code blocks

And various other cleanups

Change-Id: If945f5407036e73db980cafd2185359a488a0ff1
diff --git a/docs/release-notes/release-notes-0.6.5.rst b/docs/release-notes/release-notes-0.6.5.rst
index a9e6ac7..62af06d 100644
--- a/docs/release-notes/release-notes-0.6.5.rst
+++ b/docs/release-notes/release-notes-0.6.5.rst
@@ -3,8 +3,8 @@
 
 Release date: February 4, 2019
 
-New features:
-^^^^^^^^^^^^^
+New features
+^^^^^^^^^^^^
 
 - More support for `NDN packet format version
   0.3 <https://named-data.net/doc/NDN-packet-spec/0.3/>`__ (:issue:`4527`)
@@ -58,7 +58,7 @@
 - Reimplement ``scheduler::EventId`` with ``CancelHandle`` (:issue:`4698`)
 
 Deprecated
-~~~~~~~~~~
+^^^^^^^^^^
 
 - ``ndn-cxx/util/scheduler-scoped-event-id.hpp`` header as it is now sufficient to use
   ``ndn-cxx/util/scheduler.hpp`` header (:issue:`4698`)
@@ -66,7 +66,7 @@
 - Implicit conversion from nullptr to ``scheduler::EventId`` (:issue:`4698`)
 
 Removed
-~~~~~~~
+^^^^^^^
 
 - ``ndn::ip::address{,V6}FromString``