[tests] Update tests for msgspec 0.19.0 (#41)

per title

### Test Plan

- Run GHA, check only py38 has xfail tests

Author: nhairs

pyproject.toml

@@ -47,8 +47,7 @@ GitHub = "https://github.com/nhairs/python-json-logger"
 dev = [
     ## Optional but required for dev
     "orjson;implementation_name!='pypy'",
-    "msgspec;implementation_name!='pypy' and python_version<'3.13'",
-    "msgspec-python313-pre;implementation_name!='pypy' and python_version=='3.13'",
+    "msgspec;implementation_name!='pypy'",
     ## Lint
     "validate-pyproject[all]",
     "black",

tests/test_formatters.py

@@ -568,8 +568,14 @@ def test_common_types_encoded(
     if pythonjsonlogger.MSGSPEC_AVAILABLE and class_ is MsgspecFormatter:
         # Dataclass: https://github.com/jcrist/msgspec/issues/681
         # Enum: https://github.com/jcrist/msgspec/issues/680
-        if obj is SomeDataclass or (
-            isinstance(obj, enum.Enum) and obj in {MultiEnum.BYTES, MultiEnum.NONE, MultiEnum.BOOL}
+        # These have been fixed in msgspec 0.19.0, however they also dropped python 3.8 support.
+        # https://github.com/jcrist/msgspec/releases/tag/0.19.0
+        if sys.version_info < (3, 9) and (
+            obj is SomeDataclass
+            or (
+                isinstance(obj, enum.Enum)
+                and obj in {MultiEnum.BYTES, MultiEnum.NONE, MultiEnum.BOOL}
+            )
         ):
             pytest.xfail()