Update example for PT001 as per the new default behavior (#13019)

## Summary

Example / Use instead were not updated with the release of ruff 0.6.0.
This updates them accordingly.

crates/ruff_linter/src/rules/flake8_pytest_style/rules/fixture.rs

@@ -42,7 +42,7 @@ use super::helpers::{
 /// import pytest
 ///
 ///
-/// @pytest.fixture
+/// @pytest.fixture()
 /// def my_fixture(): ...
 /// ```
 ///
@@ -52,7 +52,7 @@ use super::helpers::{
 /// import pytest
 ///
 ///
-/// @pytest.fixture()
+/// @pytest.fixture
 /// def my_fixture(): ...
 /// ```
 ///