`SignJWTError` import moved to `@clerk/backend/errors`

The SignJWTError import path has changed from @clerk/backend to @clerk/backend/errors. You must update your import path in order for it to work correctly. Example below of the fix that needs to be made:

- import { SignJWTError } from "@clerk/backend"
+ import { SignJWTError } from "@clerk/backend/errors"