remove duplicate pytest xdist

Author: tylerriccio33

pyproject.toml

@@ -92,7 +92,6 @@ dev = [
     "pytest-rerunfailures>=15.0",
     "pytest-snapshot",
     "pytest-xdist>=3.6.1",
-    "pytest-xdist>=3.6.1",
     "quartodoc>=0.8.1; python_version >= '3.9'",
     "ruff>=0.9.9",
     "shiny>=1.4.0",