clonebundles: add missing newline to legacy response

This seems to have been removed in 6.5 (likely by 60f9602b413e).

mercurial/wireprotov1server.py

@@ -312,6 +312,7 b' def clonebundles(repo, proto):'
         if line.startswith(bundlecaches.CLONEBUNDLESCHEME):
             continue
         modified_manifest.append(line)
+    modified_manifest.append(b'')
     return wireprototypes.bytesresponse(b'\n'.join(modified_manifest))