Removed sleep and extended expected timeout.

Previously the timeout was 1 sec and the alert was delayed 500ms. With a normal execution
it seems that that 500ms diference is just not long enough to reasonably expect the alert
to appear. In reviewing this test it was shown any delay was useful and the needed time
for an alert to triggered and then recognized would need more than 500ms.

Author: emanlove

atest/acceptance/keywords/alerts.robot

@@ -43,8 +43,7 @@ Handle Alert returns message
 
 Handle Alert with custom timeout
     Click Button    Slow alert
-    Sleep  0.1s
-    Handle Alert    timeout=1s
+    Handle Alert    timeout=2s
     Click Button    Slow alert
     Run Keyword And Expect Error
     ...    Alert not found in 1 millisecond.