style: format code with Black

This commit fixes the style issues introduced in 4dd7328 according to the output
from Black.

Details: #537

pysr/sklearn_monkeypatch.py

@@ -3,7 +3,8 @@
 from sklearn.utils import validation
 
 
-def _ensure_no_complex_data(*args, **kwargs): ...
+def _ensure_no_complex_data(*args, **kwargs):
+    ...
 
 
 try:

pysr/test/test_env.py

@@ -22,9 +22,9 @@ def test_custom_shared_env(self):
                 os.environ["JULIA_DEPOT_PATH"] = tmpdir
             else:
                 old_env = os.environ["JULIA_DEPOT_PATH"]
-                os.environ["JULIA_DEPOT_PATH"] = (
-                    f"{tmpdir}:{os.environ['JULIA_DEPOT_PATH']}"
-                )
+                os.environ[
+                    "JULIA_DEPOT_PATH"
+                ] = f"{tmpdir}:{os.environ['JULIA_DEPOT_PATH']}"
             Main.eval(
                 f'pushfirst!(DEPOT_PATH, "{julia_helpers._escape_filename(tmpdir)}")'
             )