Move heterogenous->heterogeneous to the rare dictionary

"heterogenous" is both a valid word with a distinct meaning,
and an accepted alternative spelling of "heterogeneous"
(see <>)
so it is removed from the main substitutions dictionary.

However, "heterogenous" is much rarer in practice than "heterogeneous":
- [google ngram viewer](
- [4M search results]( for "heterogenous", vs
  [111M search results]( for "heterogeneous" it is added to the rare dictionary as word that is valid, but likely to be a typo.
2 files changed