Weird import behaviour of digital modules

[Yuval Langer]

In this commit I have the WEIRDEST behaviour:

https://codeberg.org/kakafarm/guile-srfi-189/commit/6e72cc50cc6b068de726f6e97b249a5af26d883c

When I run the following command at the repository worktree root:

```
guix shell -C guile -- guile -L . test-guile.scm
```

all tests pass, but at line 24 of test-body.scm we have:

```
(import (srfi 189))
```

and that should not work on Guile, right?  That's why we have SRFIs
located at `(srfi srfi-189)`, no?

Thank you,
Yuval Langer.