It is actually possible that goblins, the way they have been represented in hundreds of years of European folklore, are an antisemitic trope. Antisemitism is one of the oldest forms of prejudice after misogyny. But I don't think any individual author can really be blamed for including in their books a fairytale creature and depicting it consistently with how it has been depicted in literature since time immemorial. Even if the first person who depicted goblins in that way was antisemitic, how are we supposed to know that hundreds of years later?
As potentially offensive tropes in Harry Potter go, I'd have said the leprechauns were a more obvious one. But if you complain about the leprechauns in Harry Potter (who appeared in the context of Ireland winning the quidditch world cup and everyone being delighted about it, which strikes me as a pretty positive depiction of the Irish), people are going to think you are being silly.
If you want to cancel someone, "antisemitic" is the accusation you go with. Even if it's completely untrue.