`throwOnError` is still on `MutationObserverOptions`

[AlexErrant]

query/packages/query-core/src/types.ts

Line 1079 in 4a0a129

throwOnError?: boolean | ((error: TError) => boolean)

I believe this should be removed since it doesn't do anything (I think) and is confusing to new users like me.

Then mutate would return nothing, mutateAsync would return a promise and throwOnError can be removed. Src.

Would you accept a PR removing it, or is there a reason it's still there?