No, apparently there was no 2.2.1 or 2.2.2. I shouldn't have tried counting. Anyways, it's just a bugfix release:

2.2.3:
Bugfixes
- NameSpace#set accepted symbols, but Namespace#get would lose them.
Now symbol keys are fetched based on symbol.to_s
- Undefined iterators were triggering warnings with the -w flag