libc++ release notes: drop in-progress warnings; minor cleanups

Author: zmodem

libcxx/docs/ReleaseNotes.rst

@@ -1,19 +1,13 @@
-=========================================
-Libc++ 11.0.0 (In-Progress) Release Notes
-=========================================
+===========================
+Libc++ 11.0.0 Release Notes
+===========================
 
 .. contents::
    :local:
    :depth: 2
 
 Written by the `Libc++ Team <https://libcxx.llvm.org>`_
 
-.. warning::
-
-   These are in-progress notes for the upcoming libc++ 11 release.
-   Release notes for previous releases can be found on
-   `the Download Page <https://releases.llvm.org/download.html>`_.
-
 Introduction
 ============
 
@@ -27,19 +21,10 @@ be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.
 For more information about libc++, please see the `Libc++ Web Site
 <https://libcxx.llvm.org>`_ or the `LLVM Web Site <https://llvm.org>`_.
 
-Note that if you are reading this file from a Git checkout or the
-main Libc++ web page, this document applies to the *next* release, not
-the current one. To see the release notes for a specific release, please
-see the `releases page <https://llvm.org/releases/>`_.
-
 What's New in Libc++ 11.0.0?
 ============================
 
 New Features
 ------------
 
 - ``<numbers>``
-
-API Changes
------------
-- ...