[questions][ui] fix contribute button (#480)

apps/portal/src/components/questions/forms/ContributeQuestionForm.tsx

@@ -278,6 +278,7 @@ export default function ContributeQuestionForm({
             </button>
             <Button
               className="bg-primary-600 hover:bg-primary-700 focus:ring-primary-500 inline-flex w-full justify-center rounded-md border border-transparent px-4 py-2 text-base font-medium text-white shadow-sm focus:outline-none focus:ring-2 focus:ring-offset-2 disabled:bg-slate-400 sm:ml-3 sm:w-auto sm:text-sm"
+              disabled={!checkedSimilar}
               label="Contribute"
               type="submit"
               variant="primary"></Button>