chore(deps): Update the directories dependency to 6.0.0 (#2982)

Update the `directories` dependency to the latest and final version,
6.0.0.

The SemVer-breaking change in `directories` 6 is just that `dirs-sys` is
updated to 0.5, which, in turn, is just due to [updating some
platform-specific
dependencies](dirs-dev/dirs-sys-rs@f369f09...8bcd4aa).
There are therefore no API changes we need to worry about here.

Note that (as for [`dirs`](https://github.com/dirs-dev/dirs-rs)) the
[repository for `directories` is
archived](https://github.com/dirs-dev/directories-rs), so it might be
time to start thinking about a maintained alternative.

## Checks
- [x] I am happy for maintainers to push small adjustments to this PR,
to speed up the review cycle
- [x] I have checked that there are no existing pull requests for the
same thing

Author: musicinmybrain

Cargo.lock

@@ -24,7 +24,7 @@ time = { version = "0.3.36", features = [
 ] }
 clap = { version = "4.5.7", features = ["derive"] }
 config = { version = "0.15.8", default-features = false, features = ["toml"] }
-directories = "5.0.1"
+directories = "6.0.0"
 eyre = "0.6"
 fs-err = "3.1"
 interim = { version = "0.2.0", features = ["time_0_3"] }