Fixed typo in flash message when creating new problem
Fixed typo in flash message when creating new problem

noellekimiko/HMC-Grader,CSGreater-Developers/HMC-Grader,CSGreater-Developers/HMC-Grader,noellekimiko/HMC-Grader,noellekimiko/HMC-Grader,noellekimiko/HMC-Grader,noellekimiko/HMC-Grader,CSGreater-Developers/HMC-Grader,CSGreater-Developers/HMC-Grader,noellekimiko/HMC-Grader,CSGreater-Developers/HMC-Grader