Optimized the comparison for checked values

Editor assessment

The subject states the improvement: the comparison of checked values in useCheckboxGroup was optimized. The useCheckboxGroup scope is a proper hook noun, the fix type is defensible for a performance correction, and both the hook and the optimized operation are named. There is no body, acceptable for a small internal optimization whose headline is complete, though the approach and the measured benefit are unstated. No footers appear. The past-tense optimized is a minor mood note on a clear message. A body line on the technique or the measured win would have added real teaching value.