Don't use IPython.utils.warn (Deprecated).

And InlineBackaedConfig was renamed in  0.12 (2011):

`https://github.com/ipython/ipython/pull/923`

So we can likely remove the warning.

Author: Carreau

config.py

@@ -13,12 +13,10 @@
 # Imports
 #-----------------------------------------------------------------------------
 
-from traitlets.config import Config
 from traitlets.config.configurable import SingletonConfigurable
 from traitlets import (
     Dict, Instance, Set, Bool, TraitError, Unicode
 )
-from IPython.utils.warn import warn
 
 #-----------------------------------------------------------------------------
 # Configurable for inline backend options
@@ -41,12 +39,6 @@ class InlineBackendConfig(SingletonConfigurable):
 class InlineBackend(InlineBackendConfig):
     """An object to store configuration of the inline backend."""
 
-    def _config_changed(self, name, old, new):
-        # warn on change of renamed config section
-        if new.InlineBackendConfig != getattr(old, 'InlineBackendConfig', Config()):
-            warn("InlineBackendConfig has been renamed to InlineBackend")
-        super(InlineBackend, self)._config_changed(name, old, new)
-
     # The typical default figure size is too large for inline use,
     # so we shrink the figure size to 6x4, and tweak fonts to
     # make that fit.