update implicit root docs (#1869)

As of astral-sh/ruff#21817, ./tests are no
longer implicitly included.

Author: Gankra

docs/modules.md

@@ -27,8 +27,8 @@ then set [`environment.root`](./reference/configuration.md#root) in your `pyproj
 root = ["./app"]
 ```
 
-Note that `python` and `tests` folders are automatically added to the project `root` if they exist,
-and if they are not packages themselves (i.e. they do not contain an `__init__.py` file or an
+Note that a `./python` folder is automatically added to the project `root` if it exists,
+and is not itself a package (i.e. does not contain an `__init__.py` file or an
 `__init__.pyi` file).
 
 ## Third-party modules