Suppress nonsense DeprecationWarning caused by unittest

`unittest.TestCase.assertWarns` in context-manager form has an awkward
habit of sticking a `__warningregistry__` attribute on every module in
existence, then querying the modules for it later.  This interacts
poorly with a Numpy 2 deprecation warning trigger for code that's
attempting to import functions from modules that became private in Numpy
2.

This simply suppresses that particular warning from the test suite.

test/utils/base.py

@@ -204,6 +204,18 @@ def setUpClass(cls):
         warnings.filterwarnings("error", category=DeprecationWarning)
         warnings.filterwarnings("error", category=QiskitWarning)
 
+        # Numpy 2 made a few new modules private, and have warnings that trigger if you try to
+        # access attributes that _would_ have existed.  Unfortunately, Python's `unittest` has a
+        # tendency to add `__warningregistry__` attributes on every module in existence when we
+        # enter a `TestCase.assertWarns` context manager, which can then trick Numpy into sending
+        # out a nonsense `DeprecationWarning`.
+        warnings.filterwarnings(
+            "ignore",
+            category=DeprecationWarning,
+            message="__warningregistry__",
+            module=r"numpy(\.\w+)*",
+        )
+
         # We only use pandas transitively through seaborn, so it's their responsibility to mark if
         # their use of pandas would be a problem.
         warnings.filterwarnings(