Hey Rhonda,
Thanks for reaching out to us!
I just tested out the snippet and it appears to be working as expected on my local install. When updating the array to match the slugs from the categories that you’re wanting to hide, make sure you’re updating in the actual snippet and not the note for the snippet at the top. I realize the wording there in the note for the snippet could be a little confusing on that front.
Also, this snippet will just hide it from the main calendar. You should still be able to access the category archive for that category so the link you provided as an example will still be accessible.
Let me know if this helps.
Thanks!