fix javadoc typo

Author: davidmoten

src/main/java/rx/Producer.java

@@ -23,7 +23,7 @@ public interface Producer {
     /**
      * Request a certain maximum number of items from this Producer. This is a way of requesting backpressure.
      * To disable backpressure, pass {@code Long.MAX_VALUE} to this method.
-     * * <p>
+     * <p>
      * Requests are additive but if a sequence of requests totals more than {@code Long.MAX_VALUE} then 
      * {@code Long.MAX_VALUE} requests will be actioned and the extras <i>may</i> be ignored. Arriving at 
      * {@code Long.MAX_VALUE} by addition of requests cannot be assumed to disable backpressure. For example,