Updated Dicts concept about.md

Made same spelling change to the concept about.md, which uses the same code examples.

Author: BethanyG

concepts/dicts/about.md

@@ -172,7 +172,7 @@ You can change an entry `value` by assigning to its _key_:
 New `key`:`value` pairs can be _added_ in the same fashion:
 
 ```python
-# Adding an new "color" key with a new "tawney" value.
+# Adding a new "color" key with a new "tawney" value.
 >>> bear["color"] = 'tawney'
 {'name': 'Grizzly Bear', 'speed': 40, 'land_animal': True, 'color': 'tawney'}