Fix: assert deprecation. (opensearch-project#572)

Signed-off-by: dblock <dblock@amazon.com>

Author: dblock

test_opensearchpy/test_serializer.py

@@ -111,9 +111,7 @@ def test_serializes_numpy_floats(self) -> None:
             np.float32,
             np.float64,
         ):
-            self.assertRegexpMatches(
-                ser.dumps({"d": np_type(1.2)}), r'^\{"d":1\.2[\d]*}$'
-            )
+            self.assertRegex(ser.dumps({"d": np_type(1.2)}), r'^\{"d":1\.2[\d]*}$')
 
     def test_serializes_numpy_datetime(self) -> None:
         requires_numpy_and_pandas()