List the released, rather than pre-release package [Skip CI]

Author: nblumhardt

README.md

@@ -1,4 +1,4 @@
-# Serilog.Sinks.Async [![Build status](https://ci.appveyor.com/api/projects/status/gvk0wl7aows14spn?svg=true)](https://ci.appveyor.com/project/serilog/serilog-sinks-async) [![NuGet](https://img.shields.io/nuget/vpre/Serilog.Sinks.Async.svg?maxAge=2592000)](https://www.nuget.org/packages/Serilog.Sinks.Async) [![Join the chat at https://gitter.im/serilog/serilog](https://img.shields.io/gitter/room/serilog/serilog.svg)](https://gitter.im/serilog/serilog)
+# Serilog.Sinks.Async [![Build status](https://ci.appveyor.com/api/projects/status/gvk0wl7aows14spn?svg=true)](https://ci.appveyor.com/project/serilog/serilog-sinks-async) [![NuGet](https://img.shields.io/nuget/v/Serilog.Sinks.Async.svg)](https://www.nuget.org/packages/Serilog.Sinks.Async) [![Join the chat at https://gitter.im/serilog/serilog](https://img.shields.io/gitter/room/serilog/serilog.svg)](https://gitter.im/serilog/serilog)
 
 An asynchronous wrapper for other [Serilog](https://serilog.net) sinks. Use this sink to reduce the overhead of logging calls by delegating work to a background thread. This is especially suited to non-batching sinks like the [File](https://github.com/serilog/serilog-sinks-file) and [RollingFile](https://github.com/serilog-serilog-sinks-rollingfile) sinks that may be affected by I/O bottlenecks.
 
@@ -32,8 +32,6 @@ Because the memory buffer may contain events that have not yet been written to t
 
 ### Buffering
 
-This sink uses a separate worker thread to write to your sink, freeing up the calling thread to run in your app without having to wait.
-
 The default memory buffer feeding the worker thread is capped to 10,000 items, after which arriving events will be dropped. To increase or decrease this limit, specify it when configuring the async sink.
 
 ```csharp