README: remove Windows build machine, it's broken.

Author: Samy Al Bahra

README.md

@@ -1,7 +1,6 @@
 | Platform | Status |
 | -------- | ------ |
 | Linux and Mac OS X | [![Build Status](https://travis-ci.org/concurrencykit/ck.svg)](https://travis-ci.org/concurrencykit/ck)
-| Windows | [![Build Status](https://tea-ci.org/api/badges/concurrencykit/ck/status.svg)](https://tea-ci.org/concurrencykit/ck) |
 
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