Merge pull request #11680 from switowski/2019-04-08-store-remove-alias-doc-improvement

Update StoreMagic docstring on how to remove an alias

IPython/extensions/storemagic.py

@@ -112,6 +112,7 b' class StoreMagics(Magics):'
         python types can be safely %store'd.
 
         Also aliases can be %store'd across sessions.
+        To remove an alias from the storage, use the %unalias magic.
         """
 
         opts,argsl = self.parse_options(parameter_s,'drz',mode='string')