drop mention of puli as it is dead

Author: dbu

httplug/backwards-compatibility.rst

@@ -20,10 +20,7 @@ Discovery
 The order of the strategies is not part of our BC promise. The strategies themselves are marked
 as ``@internal`` so they are also not part of our BC promise.
 However, we do promise that we will not remove a strategy neither will we remove classes from the
-``CommonClassesStrategy``. We will also support the following Puli versions:
-
-* 1.0.0-beta9
-* 1.0.0-beta10
+``CommonClassesStrategy``.
 
 The consequences of the BC promise for the discovery library is that you can not rely on the *same* client to be
 returned in the future. However, if discovery does find a client now, you can be sure that after future updates it will still discover a client.