Fix parameter to `Thread/sleep`

[frankleonrose]

Using Clojure version 1.10.3 (and later) loading leipzig/live.clj yields error:

#future[{:status :failed, :val #error {
 :cause "No matching method sleep found taking 1 args"
 :via
 [{:type java.util.concurrent.ExecutionException
   :message "java.lang.IllegalArgumentException: No matching method sleep found taking 1 args"
   :at [java.util.concurrent.FutureTask report "FutureTask.java" 122]}
  {:type java.lang.IllegalArgumentException
   :message "No matching method sleep found taking 1 args"
   :at [clojure.lang.Reflector invokeMatchingMethod "Reflector.java" 154]}]
 :trace
 [[clojure.lang.Reflector invokeMatchingMethod "Reflector.java" 154]
  [clojure.lang.Reflector invokeStaticMethod "Reflector.java" 332]
  [leipzig.live$trickle invokeStatic "live.clj" 12]
  [leipzig.live$trickle invoke "live.clj" 10]
  [leipzig.live$play$fn__20512 invoke "live.clj" 46]
  [clojure.core$binding_conveyor_fn$fn__5772 invoke "core.clj" 2034]
  [clojure.lang.AFn call "AFn.java" 18]
  [java.util.concurrent.FutureTask run "FutureTask.java" 317]
  [java.util.concurrent.ThreadPoolExecutor runWorker "ThreadPoolExecutor.java" 1144]
  [java.util.concurrent.ThreadPoolExecutor$Worker run "ThreadPoolExecutor.java" 642]
  [java.lang.Thread run "Thread.java" 1583]]}} 0x7c738bec]

Same issue as addressed in https://github.com/overtone/overtone/issues/497