python313Packages.openshift: migrate to pythonRelaxDepsHook

pkgs/development/python-modules/openshift/default.nix

···
   six,
   python-string-utils,
   pytest-bdd,
+  pytest-cov-stub,
   pytestCheckHook,
 }:
 
···
     hash = "sha256-uLfewj7M8KNs3oL1AM18sR/WhAR2mvBfqadyhR73FP0=";
   };
 
-  postPatch = ''
-    substituteInPlace requirements.txt \
-      --replace "kubernetes ~= 12.0" "kubernetes"
-
-    sed -i '/--cov/d' setup.cfg
-  '';
+  pythonRelaxDeps = [ "kubernetes" ];
 
   propagatedBuildInputs = [
     jinja2
···
 
   nativeCheckInputs = [
     pytest-bdd
+    pytest-cov-stub
     pytestCheckHook
   ];