Fix about_classes koan

* Test on line 162 does not pass with specified 
  input.

* Tested in IRB, returns same value specified by
  the failing koan test.  Instead yields:

* about_classes.rb:162: syntax error, unexpected
  tIDENTIFIER, expecting keyword_do or '{' or '(' 
  assert_equal <Dog named 'Fido'>, fidos_self

* Commented out, to complete exercise.

[#54145689}