[Python] Reduce time before asyncronous run in JupyROOT unit test

Only waiting 0.25 seconds before printing "Asyncronous" should increase
the probability to have this string printed by the time the main thread
waits one second, which is what the unit test expects.

Author: guitargeek

bindings/jupyroot/python/JupyROOT/helpers/handlers.py

@@ -101,7 +101,7 @@ class Runner(object):
     >>> r.AsyncRun("ss");time.sleep(1)
     ss
     >>> def g(msg):
-    ...    time.sleep(.5)
+    ...    time.sleep(.25)
     ...    print(msg)
     >>> r= Runner(g, p)
     >>> r.AsyncRun("Asynchronous");print("Synchronous");time.sleep(1)