[pre-commit.ci] auto fixes from pre-commit.com hooks

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doc/en/how-to/doctest.rst

@@ -227,6 +227,7 @@ place the objects you want to appear in the doctest namespace:
     import pytest
     import numpy
 
+
     @pytest.fixture(autouse=True)
     def add_np(doctest_namespace):
         doctest_namespace["np"] = numpy