docs: correct single-test command

Co-authored-by: jaimergp <[email protected]>

README.md

@@ -144,7 +144,7 @@ pytest tests/test_configure_feedstock.py
 
 Run specific test within a file:
 ```sh
-pytest tests/test_configure_feedstock.py -k test_cuda_enabled_render
+pytest tests/test_configure_feedstock.py::test_cuda_enabled_render
 ```
 
 Run with coverage (this is how the tests are run in CI):