remove needless annotation. @Nonnull is enough.

Lombok uses regexp to check annotation, and @Nonnull is
enough to use. we do not have to annotate fields by
both of @Nonnull and @NonNull.
https://github.com/rzwitserloot/lombok/blob/f956ba1e337699206052a016da65f4f02ac6825b/src/core/lombok/core/handlers/HandlerUtil.java#L196