update comment Retryer.java (#1228)

core/src/main/java/feign/Retryer.java

@@ -83,7 +83,7 @@ public interface Retryer extends Cloneable {
      * The interval increases exponentially with each attempt, at a rate of nextInterval *= 1.5
      * (where 1.5 is the backoff factor), to the maximum interval.
      *
-     * @return time in nanoseconds from now until the next attempt.
+     * @return time in milliseconds from now until the next attempt.
      */
     long nextMaxInterval() {
       long interval = (long) (period * Math.pow(1.5, attempt - 1));