NextResponse.rewrite does not override origin server headers

### Link to the code that reproduces this issue https://github.com/Gebov/nextjs-rewrite-headers ### To Reproduce 1. Start the app 2. Request /rewrite 3. Inspect the response headers 4. Verify that the Cache-Control header is not overriden 5. Verify that the custom header is overriden ### Current vs. Expected behavior Currently the app is configured to proxy requests to nextjs.org with the URL /rewrite. I expect all the headers specified in the NextResponse.headers to be overriden. In particular the Cache-Control header. Currently it is not overriden. Custom headers work. ### Provide environment information ```bash Operating System: Platform: win32 Arch: x64 Version: Windows 11 Enterprise Available memory (MB): 32488 Available CPU cores: 16 Binaries: Node: 20.15.0 npm: N/A Yarn: N/A pnpm: N/A Relevant Packages: next: 14.2.13 // Latest available version is detected (14.2.13). eslint-config-next: N/A react: 18.3.1 react-dom: 18.3.1 typescript: N/A Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Middleware ### Which stage(s) are affected? (Select all that apply) next dev (local), next start (local) ### Additional context _No response_