Trivial refactoring to make the capsule API more user friendly. (#4720)

* Trivial refactoring to make the capsule API more user friendly.

* Use new API in production code. Thanks @Lalaland for pointing this out.

tests/test_pytypes.py

@@ -319,6 +319,19 @@ def test_capsule(capture):
     """
     )
 
+    with capture:
+        a = m.return_capsule_with_destructor_3()
+        del a
+        pytest.gc_collect()
+    assert (
+        capture.unordered
+        == """
+        creating capsule
+        destructing capsule: 1233
+        original name: oname
+    """
+    )
+
     with capture:
         a = m.return_renamed_capsule_with_destructor_2()
         del a