Closed context can still schedule timer

### Version

4.5.11

### Context

Before 4.5.11, when setTimer from context of undeployed verticle, it will raise `IllegalStateException`, which could prevent new timer from being scheduled on the undeployed verticle.
However, with this line of change in 4.5.11, it no longer throws exception in this case and the timer could still be scheduled on this closed context:
https://github.com/eclipse-vertx/vert.x/pull/5344/files#diff-554a5d78ab4ac2cc98730e43ec55bb7f39f27fcbe22a1e6a7f4e6d7f9734b4eeR56

### Do you have a reproducer?

Tried write a unit test in `TimerTest`:
```java
@Test
public void testUndeployWhenSchedulingTimer() throws InterruptedException {
waitFor(2);
AtomicLong timer = new AtomicLong(-1);
AtomicReference deploymentID = new AtomicReference<>();
CountDownLatch deployLatch = new CountDownLatch(2);
CountDownLatch undeployLatch = new CountDownLatch(1);
vertx.deployVerticle(new AbstractVerticle() {
@Override
public void start() {
context.executeBlocking(() -> {
deployLatch.countDown();
try {
undeployLatch.await();
} catch (InterruptedException e) {
// Ignore
}
try {
timer.set(vertx.setTimer(10, id2 -> {
fail("Should not be called");
}));
} catch (IllegalStateException e) {
complete();
}
return null;
}, true)
.onComplete(onSuccess(v -> {}));
}
}, onSuccess(deployment -> {
deploymentID.set(deployment);
deployLatch.countDown();
}));

deployLatch.await();
vertx.undeploy(deploymentID.get(), onSuccess(v -> {
undeployLatch.countDown();
complete();
}));
await();
assertEquals(-1, timer.get());
}
```
It passed on 4.5.10 but failed on 4.5.11 with:
```
Starting test: TimerTest#testUndeployWhenSchedulingTimer
java.lang.AssertionError: Should not be called
at org.junit.Assert.fail(Assert.java:89)
at io.vertx.test.core.AsyncTestBase.fail(AsyncTestBase.java:268)
at io.vertx.core.TimerTest.access$2100(TimerTest.java:37)
at io.vertx.core.TimerTest$6.lambda$start$0(TimerTest.java:478)
at io.vertx.core.impl.VertxImpl$InternalTimerHandler.handle(VertxImpl.java:1092)
at io.vertx.core.impl.VertxImpl$InternalTimerHandler.handle(VertxImpl.java:1063)
at io.vertx.core.impl.ContextImpl.emit(ContextImpl.java:342)
at io.vertx.core.impl.ContextImpl.emit(ContextImpl.java:335)
at io.vertx.core.impl.ContextInternal.emit(ContextInternal.java:200)
at io.vertx.core.impl.VertxImpl$InternalTimerHandler.run(VertxImpl.java:1081)
at io.netty.util.concurrent.PromiseTask.runTask(PromiseTask.java:98)
at io.netty.util.concurrent.ScheduledFutureTask.run(ScheduledFutureTask.java:156)
at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:173)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:166)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.base/java.lang.Thread.run(Thread.java:829)
Unhandled exception
```

### Extra

I'm not even sure if it is intended to not fail the setTimer in this case...
I did not find explanation on why this exception was removed and how to better handle undeploy case after this change.