Bug Fix: Hook into `init` rather than `plugins_loaded` for VIP Search versioning’s delete handlers

Previously VIP Search registered actions to handle deleted content during plugins_loaded, but this is too early as some Indexables may not have been registered yet. VIP Search sets up Features (and their Indexables) on init, which comes later.

https://github.com/Automattic/vip-go-mu-plugins/pull/1903