test: make pass when run on Node.js >22.13

After nodejs/node#55816, getMaxListeners() throws by default
when called on AbortSignal.
Turns out that it's not necessary to use it, just any value will do
as the test guarantees that there's a single listener anyway.

src/completion-listener.spec.ts

@@ -1,4 +1,4 @@
-import { getEventListeners, getMaxListeners } from 'events';
+import { getEventListeners } from 'events';
 import { TestScheduler } from 'rxjs/testing';
 
 import { CloseEvent } from './command';
@@ -59,9 +59,8 @@ describe('listen', () => {
 
     it('does not leak memory when listening for abort signals', () => {
         const abortCtrl = new AbortController();
-        const maxListeners = getMaxListeners(abortCtrl.signal);
         createController().listen(
-            Array.from({ length: maxListeners + 1 }, () => new FakeCommand()),
+            Array.from({ length: 10 }, () => new FakeCommand()),
             abortCtrl.signal,
         );
         expect(getEventListeners(abortCtrl.signal, 'abort')).toHaveLength(1);