Suppress nonsense DeprecationWarning caused by unittest

`unittest.TestCase.assertWarns` in context-manager form has an awkward
habit of querying the `__warningregistry__` attribute on every module in
existence.  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, if a warning has previously been triggered
out of `numpy.linalg._linalg`.

This simply suppresses that particular warning from the test suite.

test/utils/base.py

@@ -204,6 +204,20 @@ 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 `warnings` module
+        # adds a field called `__warningregistry__` to any module that triggers a warning, and
+        # `unittest.TestCase.assertWarns` then queries said fields on all existing modules.  On
+        # macOS ARM, we see some (we think harmless) warnings come out of `numpy.linalg._linalg` (a
+        # now-private module) during transpilation, which means that subsequent `assertWarns` calls
+        # can spuriously 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(