Error parsing headers when downloading binary

I'm getting an error downloading the binary when trying to start up a test server

```
_, err := testserver.NewTestServer()

if err != nil {
panic(err)
}
```

```
GET https://edge-binaries.cockroachdb.com/cockroach/cockroach.darwin-amd64.LATEST
Failed to fetch latest binary: error parsing Content-Disposition headers map[Accept-Ranges:[bytes] Age:[0] Alt-Svc:[h3=":443"; ma=2592000,h3-29=":443"; ma=2592000] Cache-Control:[no-cache,public,max-age=3600] Content-Length:[185562128] Content-Type:[application/octet-stream] Date:[Wed, 28 Dec 2022 20:23:01 GMT] Etag:["d2e43af9be2469a905d71c777b6b7727"] Last-Modified:[Wed, 28 Dec 2022 19:00:16 GMT] Server:[UploadServer] X-Goog-Generation:[1672254016424452] X-Goog-Hash:[crc32c=mC0r2g== md5=0uQ6+b4kaakF1xx3e2t3Jw==] X-Goog-Metageneration:[2] X-Goog-Storage-Class:[STANDARD] X-Goog-Stored-Content-Encoding:[identity] X-Goog-Stored-Content-Length:[185562128] X-Guploader-Uploadid:[ADPycdthy1breMpK_xtwPITgJN4EZMo0Hks_2Mfstr71vWpBFY2efhDwmzSJEci5ak8DfePemBLOI9J2Nb7rvUw9-x9c0Q]]: mime: no media type, attempting to use cockroach binary from your PATH
```

Looking at the code, it seems like it's trying parse a filename from the content-disposition header. But looking at the headers for that URL, it seems like there's no content-disposition header? I'm not sure if something changed on the cockroach db server side? Or maybe there's something that I'm doing wrong here