onEvent('recipes', event => { event.remove({output: 'ironjetpacks:gold_jetpack'}) })

Doesn't remove the recipe, reloads with no errors, script in server_scripts folder

I believe that Iron Jetpack recipes either do not use the vanilla recipe manager, or are hard coded

There have been issues in the past

for example:

sure looks like it, iron jetpacks apparently uses it's own "recipe manager" that can dynamically make the recipes from a given material, so pretty much hard coded