Remove dead files

You don't need a MANIFEST.in file when using pbr, and the announce.rst
file wasn't referenced anywhere and has been effectively replaced by
reno.

Change-Id: Ib40d6f194a47901487c4fca1220dad7002d31984
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

MANIFEST.in

@@ -1,5 +0,0 @@
-include setup.py
-recursive-include docs *.rst *.py *.html *.css *.js *.png *.txt *.jpg
-recursive-include tests *.py
-include tox.ini
-include LICENSE

announce.rst

@@ -1,38 +0,0 @@
-================
- stevedore 0.14
-================
-
-.. tags:: stevedore release python
-
-What is stevedore?
-==================
-
-Python makes loading code dynamically easy, allowing you to configure
-and extend your application by discovering and loading extensions
-("*plugins*") at runtime. Many applications implement their own
-library for doing this, using ``__import__`` or
-``importlib``. stevedore_ avoids creating yet another extension
-mechanism by building on top of `setuptools entry points`_. The code
-for managing entry points tends to be repetitive, though, so stevedore
-provides manager classes for implementing common patterns for using
-dynamically loaded extensions.
-
-.. _stevedore: http://stevedore.readthedocs.org
-
-.. _setuptools entry points: https://setuptools.readthedocs.io/en/latest/pkg_resources.html#convenience-api
-
-
-What's New?
-===========
-
-- Provide an option to control requirements checking when loading
-  plugins, and disable it by default. This removes protection against
-  loading the wrong version of a plugin, or that plugin's
-  dependencies.
-
-
-Installing
-==========
-
-Visit the stevedore_ project page for download links and installation
-instructions.