OptionalSubscriptsTests.Pond™ test_versioning

The unit test for Pond is failing as it's attempting to reference a source which no longer exists

```
OptionalSubscripts/Pond.swift:151: Fatal error: 😱 Reference counting (-1) of non existent source 'v/1.0/way/to'
2022-12-05 17:59:22.761168+0000 xctest[28457:4759328] OptionalSubscripts/Pond.swift:151: Fatal error: 😱 Reference counting (-1) of non existent source 'v/1.0/way/to'
```