Remove unrequired shutdown from example app

Author: foygl

examples/simple/src/main/java/com/bugsnag/example/simple/ExampleApp.java

@@ -61,8 +61,5 @@ public void run() {
                 throw new RuntimeException("Unhandled exception");
             }
         }).start();
-
-        // Exit to run the shutdown hooks
-        System.exit(0);
     }
 }