Update for Cabal 3.14

[penelopeysm]

And finally this one, which follows on from https://github.com/dan-t/cabal-lenses/pull/10.

I don't think the line of code I changed is being tested, since the SetupConfig tests are not being run.

https://github.com/dan-t/cabal-bounds/blob/7bb32cb23bc715c9d405f947ed5704c86dbab768/tests/Main.hs#L63-L67

That said, the other tests pass and the executable builds, and I'm reasonably certain that the change I made preserves the behaviour (it interprets the config file relative to the working directory).