Increase testSignalsKeepTheLoopRunning timer to 1.6 as it make more s…

…ense since it's supposed to run slower then 1.5, and removed $loop->stop() as that is supposed to happen once the signal listener has been removed

tests/AbstractLoopTest.php

@@ -428,9 +428,8 @@ public function testSignalsKeepTheLoopRunning()
     {
         $function = function () {};
         $this->loop->addSignal(SIGUSR1, $function);
-        $this->loop->addTimer(1.51, function () use ($function) {
+        $this->loop->addTimer(1.6, function () use ($function) {
             $this->loop->removeSignal(SIGUSR1, $function);
-            $this->loop->stop();
         });
 
         $this->assertRunSlowerThan(1.5);