Clarify a note on graph ordering in graph_atlas_g docstring (networkx#8475)

* Clarify docs on graph ordering in graph_atlas_g

+ Add a snippet to reproduce out-of-order graph indices.
+ Fix a typo in out-of-order graph index.

* Remove code example in graph_atlas_g docstring

Co-authored-by: Ross Barnowski <rossbar@caltech.edu>

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Co-authored-by: Ross Barnowski <rossbar@caltech.edu>

Author: romazu

networkx/generators/atlas.py

@@ -215,7 +215,7 @@ def graph_atlas_g():
 
     - graphs 55 and 56 with degree sequences 001111 and 000112,
     - graphs 1007 and 1008 with degree sequences 3333444 and 3333336,
-    - graphs 1012 and 1213 with degree sequences 1244555 and 1244456.
+    - graphs 1012 and 1013 with degree sequences 1244555 and 1244456.
 
     References
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