Stack traces on subgraph fetches are propagated even when `includeStacktraceInErrorResponses` is false

### Issue Description

The `includeStacktraceInErrorResponses` is written to "enrich" errors with stack traces when enabled. But it does not _redact_ stack traces when disabled. If a subgraph includes `extensions.stacktrace` in its response, that will be forwarded to clients.

This is surprising, but relatively easy to fix with a `formatError` hook:

```js
const server = new ApolloServer({
gateway,
includeStacktraceInErrorResponses: false,
formatError: (formatted, original) => {
// THIS SHOULDN'T BE NECESSARY
if (formatted.extensions?.stacktrace) {
delete formatted.extensions.stacktrace;
}
return formatted;
},
});
```

### Link to Reproduction

https://github.com/lennyburdette/curly-succotash/blob/main/gateway.js#L14

### Reproduction Steps

_No response_

Start with the gateway.js reproduction linked in the issue and trace how ApolloServer handles subgraph errors when includeStacktraceInErrorResponses is false. Confirm the behavior with the supplied gateway configuration; done means subgraph extensions.stacktrace values are not forwarded to clients when stack traces are disabled.

Written by the indexing model from the issue text.