doc: fix pytest_load_initial_conftests example referring to conftest.py

changelog/4482.doc.rst

@@ -0,0 +1,5 @@
+Corrected the "Dynamically adding command line options" example so it no longer
+refers to the ``pytest_load_initial_conftests`` hook as living in a
+``conftest.py``. As noted in the hook reference, ``pytest_load_initial_conftests``
+is not called for ``conftest.py`` files and must be provided by an installable
+plugin.

doc/en/example/simple.rst

@@ -229,7 +229,7 @@ the command line arguments before they get processed:
 If you have the :pypi:`xdist plugin <pytest-xdist>` installed
 you will now always perform test runs using a number
 of subprocesses close to your CPU. Running in an empty
-directory with the above conftest.py:
+directory with the above plugin:
 
 .. code-block:: pytest