Update xblock-utils to v1.0.3.
Update xblock-utils to v1.0.3.

New version includes fixes from https://github.com/edx/xblock-utils/pull/38 and https://github.com/edx/xblock-utils/pull/39.

proversity-org/problem-builder,proversity-org/problem-builder,proversity-org/problem-builder