Clean up release notes post-ocata release

Cleans up release note index since ocata release has been cut.

Change-Id: I4e6576bbdf492dd0c10cc1d550e3462fc5f9f6ef

releasenotes/source/index.rst

@@ -5,7 +5,8 @@ Ironic Python Agent Release Notes
 .. toctree::
    :maxdepth: 1
 
-   Current Series <current-series>
-   Newton <newton>
-   Mitaka <mitaka>
-   Liberty <liberty>
+   unreleased
+   ocata
+   newton
+   mitaka
+   liberty

releasenotes/source/liberty.rst

@@ -1,6 +1,6 @@
-============================
-Liberty Series Release Notes
-============================
+============================================
+Liberty Series (1.0.0 - 1.0.x) Release Notes
+============================================
 
 .. release-notes::
    :branch: origin/stable/liberty

releasenotes/source/mitaka.rst

@@ -1,6 +1,6 @@
-===========================
-Mitaka Series Release Notes
-===========================
+===========================================
+Mitaka Series (1.1.0 - 1.2.x) Release Notes
+===========================================
 
 .. release-notes::
    :branch: origin/stable/mitaka

releasenotes/source/newton.rst

@@ -1,6 +1,6 @@
-============================
- Newton Series Release Notes
-============================
+===========================================
+Newton Series (1.3.0 - 1.5.x) Release Notes
+===========================================
 
 .. release-notes::
    :branch: origin/stable/newton

releasenotes/source/ocata.rst

@@ -0,0 +1,6 @@
+==========================================
+Ocata Series (2.0.0 - 2.0.x) Release Notes
+==========================================
+
+.. release-notes::
+   :branch: origin/stable/ocata