Function URL with Response Streaming does not support Content-Encoding

If I compress my response using `gzip` and set a proper `Content-Encoding` response header, it appears like Function URL will decompress my response on-the-fly, remove the `Content-Encoding` header, and pass down the uncompressed response stream. This is wasteful and unnecessary.

```js
const pipeline = require("util").promisify(require("stream").pipeline);
const { Readable } = require("stream");
const zlib = require('zlib');

exports.handler = awslambda.streamifyResponse(async (event,
responseStream, context) => {
responseStream = awslambda.HttpResponseStream.from(responseStream, {
statusCode: 200,
headers: {
'content-encoding': 'gzip',
'content-type': 'text/plain',
}
});

await pipeline(
Readable.from(zlib.gzipSync('hello world')),
responseStream,
);
});
```

See here - the response is uncompressed, with `Content-Encoding` header stripped: