It’s intentional; the release notes indicate it was eliminated in favor of using MQTT Device Trigger or a State Trigger with an event entity. The following helpful topic explains how to use an event entity.
If you’re not quite ready, or don’t have time, to modify your automations to work the new way, there are posts in that topic showing how to enable the “Home Assistant legacy action sensors” option (so your existing automations continue to work). Then you can convert your automations whenever it’s more convenient for you.