submodule: dependencies/cassette references a non-existent commit

[GiscardBiamby]

https://github.com/ChrisMH/Cassette.Nancy/commit/62eccd3356a7aca3c694873e58ca7691be3033ef

This points the submodule to commit hash f46ca7076e855472725dc0018840b3d9f64e4697, which doesn't exist in the Cassette repo.

As a result, when someone does a fresh clone of Cassette.Nancy, Visual Studio fails to load some of the projects.