Ensure RSC is detecting correctly during revalidate (#42508)

Fixes: #42504

Patch tested against provided reproduction here
https://portfolio-pcmtikvrv-ijjk-testing.vercel.app/

## Bug

- [x] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the
feature request has been accepted for implementation before opening a
PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)

packages/next/server/base-server.ts

@@ -484,13 +484,9 @@ export default abstract class Server<ServerOptions extends Options = Options> {
       if (typeof parsedUrl.query === 'string') {
         parsedUrl.query = parseQs(parsedUrl.query)
       }
-      // in minimal mode we detect RSC revalidate if the .rsc path is requested
-      if (
-        this.minimalMode &&
-        (req.url.endsWith('.rsc') ||
-          (typeof req.headers['x-matched-path'] === 'string' &&
-            req.headers['x-matched-path'].endsWith('.rsc')))
-      ) {
+      // in minimal mode we detect RSC revalidate if the .rsc
+      // path is requested
+      if (this.minimalMode && req.url.endsWith('.rsc')) {
         parsedUrl.query.__nextDataReq = '1'
       }