Fix example pyproject.toml in project concept documentation (#9298)

The snippet out of context looks like a valid minimal pyproject.toml
which it is not without name and version. The line worked in layout.md
before when it was just under the minimal config.

---------

Co-authored-by: Zanie Blue <[email protected]>

Author: jooon

docs/concepts/projects/config.md

@@ -7,8 +7,10 @@ field of the `pyproject.toml`.
 
 It is recommended to set a `requires-python` value:
 
-```toml title="pyproject.toml"
+```toml title="pyproject.toml" hl_lines="4"
 [project]
+name = "example"
+version = "0.1.0"
 requires-python = ">=3.12"
 ```