TST use global_dtype in sklearn/cluster/tests/test_birch.py (#22671)
TST use global_dtype in sklearn/cluster/tests/test_birch.py (#22671)

Co-authored-by: Olivier Grisel <2debdaedc015a28b6d296a878ea9501beb58cbd4@ensta.org>
Co-authored-by: Jérémie du Boisberranger <e3f2e912120bf2b3b91d0d3b53109753fb66c284@users.noreply.github.com>
scikit-learn/scikit-learn,betatim/scikit-learn,scikit-learn/scikit-learn,betatim/scikit-learn,betatim/scikit-learn,scikit-learn/scikit-learn,betatim/scikit-learn,scikit-learn/scikit-learn