`top_level.txt` include a non existing module `src`

Current content of `top_level.txt` in dist metadata is:

```

kiwisolver

src

```

This causes [importlib.metadata.packages_distributions()](https://docs.python.org/3.11/library/importlib.metadata.html#mapping-import-to-distribution-packages) to return:

```python

{

  'kiwisolver': ['kiwisolver'],

  'src': ['kiwisolver'],

  ...

}

```

This is confusing, especially in the src-layout project, whose top-level package happens to be `src`.



Please consider this change, though this will add `tests` directory into source distribution (hope this is not important):

```diff

diff --git a/pyproject.toml b/pyproject.toml

index 26dee95..3440a23 100644

--- a/pyproject.toml

+++ b/pyproject.toml

@@ -48,8 +48,7 @@ include-package-data = false

 package-data = {kiwisolver = ["py.typed", "*.pyi"]}



 [tool.setuptools.packages.find]

-where = ["py"]

-exclude = ["tests"]

+include = ["py/kiwisolver"]



 [tool.setuptools_scm]

 write_to = "py/src/version.h"

```

[]