Remove unused code

Author: ivancea

server/src/main/java/org/elasticsearch/common/logging/HeaderWarning.java

@@ -426,10 +426,4 @@ static void addWarning(Set<ThreadContext> threadContexts, String message, Object
             }
         }
     }
-
-    static void addRawWarning(Set<ThreadContext> threadContexts, String warningHeader) {
-        for (ThreadContext threadContext : threadContexts) {
-            threadContext.addResponseHeader("Warning", warningHeader);
-        }
-    }
 }