fixing a typo in testing code

Author: lucianoviana

artio-binary-entrypoint-system-tests/src/test/java/uk/co/real_logic/artio/system_tests/BinaryEntryPointClient.java

@@ -206,7 +206,7 @@ private <T extends MessageDecoderFlyweight> T readInternal(final T messageDecode
             final int readHeader = readSocket();
             if (readHeader != headerLength)
             {
-                throw new IllegalStateException("readHeader=" + readHeader + ",headerLength" + headerLength);
+                throw new IllegalStateException("readHeader=" + readHeader + ",headerLength=" + headerLength);
             }
 
             final int totalLength = readSofh(unsafeReadBuffer, 0, BINARY_ENTRYPOINT_TYPE);