The checked answer does work but officially in MongooseJS latest, you should use pull.
doc.subdocs.push({ _id: 4815162342 }) // added
doc.subdocs.pull({ _id: 4815162342 }) // removed
https://mongoosejs.com/docs/api.html#mongoosearray_MongooseArray-pull
I was just looking that up too.
See Daniel's answer for the correct answer. Much better.