test(nextjs): Use RC1 as latest for Next.js canary tests (#13995)

Author: lforst

dev-packages/e2e-tests/test-applications/nextjs-15/package.json

@@ -9,7 +9,8 @@
     "test:dev": "TEST_ENV=development playwright test",
     "test:build": "pnpm install && npx playwright install && pnpm build",
     "test:build-canary": "pnpm install && pnpm add next@canary && pnpm add react@beta && pnpm add react-dom@beta && npx playwright install && pnpm build",
-    "test:build-latest": "pnpm install && pnpm add next@rc && pnpm add react@beta && pnpm add react-dom@beta && npx playwright install && pnpm build",
+    "//": "15.0.0-canary.194 is the canary release attached to Next.js RC 1. We need to use the canary version instead of the RC because PPR will not work without. The specific react version is also attached to RC 1.",
+    "test:build-latest": "pnpm install && pnpm add next@15.0.0-canary.194 && pnpm add react@19.0.0-rc-cd22717c-20241013 && pnpm add react-dom@19.0.0-rc-cd22717c-20241013 && npx playwright install && pnpm build",
     "test:assert": "pnpm test:prod && pnpm test:dev"
   },
   "dependencies": {