Restore *.pxd files in ucxx wheel (#270)

`*.pxd` files were mistakenly removed in #260. Resume installing them in the ucxx wheel.

Authors:
  - Kyle Edwards (https://github.com/KyleFromNVIDIA)

Approvers:
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: #270

python/ucxx/pyproject.toml

@@ -73,7 +73,7 @@ ninja.make-fallback = true
 sdist.exclude = ["*tests*"]
 sdist.reproducible = true
 wheel.packages = ["ucxx"]
-wheel.exclude = ["*.pyx", "*.pxd", "CMakeLists.txt"]
+wheel.exclude = ["*.pyx", "CMakeLists.txt"]
 
 [tool.scikit-build.metadata.version]
 provider = "scikit_build_core.metadata.regex"