Fix: spelling on PlotlyDataTypeError message

Author: Patrick Burris

Diff for: plotly/exceptions.py

@@ -122,7 +122,7 @@ def __init__(self, obj, path, notes=()):
         format_dict = {'index': path[-1], 'object_name': obj._name}
         message = ("Invalid entry found in '{object_name}' at index, '{index}'"
                    .format(**format_dict))
-        note = "It's invalid because it does't contain a valid 'type' value."
+        note = "It's invalid because it doesn't contain a valid 'type' value."
         notes = [note] + list(notes)
         super(PlotlyDataTypeError, self).__init__(
             message=message, path=path, notes=notes