Remove filter for openapi-core

Effectively revert commit 4ddcdea: the PR referenced merged a long time
ago.

Signed-off-by: Stephen Finucane <stephen@that.guru>

Author: stephenfin

patchwork/tests/__init__.py

@@ -13,15 +13,3 @@
 # configure warnings
 
 warnings.simplefilter('once', DeprecationWarning)
-
-# TODO: Remove this once [1] merges and is released
-# [1] https://github.com/p1c2u/openapi-core/pull/395
-warnings.filterwarnings(
-    'ignore',
-    message=(
-        'The distutils package is deprecated and slated for removal in Python '
-        '3.12. Use setuptools or check PEP 632 for potential alternatives'
-    ),
-    module='openapi_core',
-    category=DeprecationWarning,
-)