Huggingface GIT returns null as Content-Type instead of application/x-git-receive-pack-result

### Describe the bug

We push changes to our datasets programmatically. Our git client jGit reports that the hf git server returns null as Content-Type after a push.

### Steps to reproduce the bug

A basic kotlin application:
```
val person = PersonIdent(
"padmalcom",
"padmalcom@sth.com"
)

val cp = UsernamePasswordCredentialsProvider(
"padmalcom",
"mysecrettoken"
)

val git =
KGit.cloneRepository {
setURI("https://huggingface.co/datasets/sth/images")
setTimeout(60)
setProgressMonitor(TextProgressMonitor())
setCredentialsProvider(cp)
}

FileOutputStream("./images/images.csv").apply { writeCsv(images) }
git.add {
addFilepattern("images.csv")
}

for (i in images) {
FileUtils.copyFile(
File("./files/${i.id}"),
File("./images/${i.id + File(i.fileName).extension }")
)
git.add {
addFilepattern("${i.id + File(i.fileName).extension }")
}
}

val revCommit = git.commit {
author = person
message = "Uploading images at " + LocalDateTime.now()
.format(DateTimeFormatter.ISO_DATE_TIME)
setCredentialsProvider(cp)
}

val push = git.push {
setCredentialsProvider(cp)
}
```

### Expected behavior

The git server is expected to return the Content-Type _application/x-git-receive-pack-result_.

### Environment info

It is independent from the datasets library.