Update README.md

Change to refer to the new combined build server.

README.md

@@ -9,7 +9,7 @@ Useful links
  * Download: http://download.mantidproject.org
  * Asking for help: http://download.mantidproject.org/webmailer/index.php
  * Issue tracking: http://trac.mantidproject.org/mantid/
- * Build servers: http://download.mantidproject.org/jenkins and https://builds.sns.gov/
+ * Build server: http://builds.mantidproject.org
  * Developer news: http://mantidproject.github.io/news/
 
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