fix: hide unavailable Twins Lab demo

lib/site-content.ts

@@ -536,7 +536,6 @@ export const caseStudies: CaseStudyContent[] = [
     impact:
       "Expor estados simulados do reator a uma interface autenticada e manter histórico/status do simulador.",
     stack: ["Next.js", "TypeScript", "NextAuth", "MongoDB", "SSE"],
-    demoUrl: "https://twins.evandro.dev.br",
     githubUrl: "https://github.com/evandrodevbr/twins-lab",
     detail: {
       answer: {