LibCore: Don't reserve 2 KiB of stack memory when processing event queue

The inline capacity on ThreadEventQueue::Private::queued_events caused
us to reserve (and importantly, not initialize!) 2 KiB of stack memory
when entering ThreadEventQueue::process().

This was causing any leftover pointers to GC-allocated objects within
that memory range to keep those objects alive, even when all other
references were gone.

Libraries/LibCore/ThreadEventQueue.cpp

@@ -35,7 +35,7 @@ struct ThreadEventQueue::Private {
     };
 
     Threading::Mutex mutex;
-    Vector<QueuedEvent, 128> queued_events;
+    Vector<QueuedEvent> queued_events;
     Vector<NonnullRefPtr<Promise<NonnullRefPtr<EventReceiver>>>, 16> pending_promises;
     bool warned_promise_count { false };
 };