shorten json indent to 1sp

IPython/nbformat/v2/nbjson.py

@@ -51,7 +51,7 b' class JSONWriter(NotebookWriter):'
 
     def writes(self, nb, **kwargs):
         kwargs['cls'] = BytesEncoder
-        kwargs['indent'] = 4
+        kwargs['indent'] = 1
         kwargs['sort_keys'] = True
         if kwargs.pop('split_lines', True):
             nb = split_lines(copy.deepcopy(nb))