httprepo: use content-type application/mercurial-0.1 for POST

Previously, application/octet-stream was used. The content-type is
currently ignored by the server.

mercurial/httprepo.py

@@ -231,7 +231,7 b' class httprepository(repo.repository):'
             try:
                 resp = self.do_read(
                      'unbundle', data=fp,
-                     headers={'Content-Type': 'application/octet-stream'},
+                     headers={'content-type': 'application/mercurial-0.1'},
                      heads=' '.join(map(hex, heads)))
                 resp_code, output = resp.split('\n', 1)
                 try: