fix(deps): adjust pin for typeguard

Our tests fail for various older versions or typeguard.

Author: dairiki

CHANGELOG.md

@@ -9,6 +9,9 @@
  - Tighten pin on `typing-inspect` in an attempt to prevent
    breakage from a hypothetical major version bump.
 
+ - Tighten pin on `typeguard` to exclude older versions
+   for which our tests fail.
+
 [#240]: https://github.com/lovasoa/marshmallow_dataclass/issues/240
 
 ## v8.5.13 (2023-04-20)

setup.py

@@ -22,7 +22,7 @@
         "marshmallow-enum; python_version < '3.7'",
         "marshmallow>=3.18.0,<4.0; python_version >= '3.7'",
     ],
-    "union": ["typeguard>=2.0.0,<4.0.0"],
+    "union": ["typeguard>=2.4.1,<4.0.0"],
     "lint": ["pre-commit~=2.17"],
     ':python_version == "3.6"': ["dataclasses", "types-dataclasses<0.6.4"],
     "docs": ["sphinx"],