Remove unused n_jobs

Author: WillAyd

ci/scripts/python_build.sh

@@ -39,21 +39,6 @@ if [ -n "${ARROW_PYTHON_VENV:-}" ]; then
   . "${ARROW_PYTHON_VENV}/bin/activate"
 fi
 
-case "$(uname)" in
-  Linux)
-    n_jobs=$(nproc)
-    ;;
-  Darwin)
-    n_jobs=$(sysctl -n hw.ncpu)
-    ;;
-  MINGW*)
-    n_jobs=${NUMBER_OF_PROCESSORS:-1}
-    ;;
-  *)
-    n_jobs=${NPROC:-1}
-    ;;
-esac
-
 if [ -n "${CONDA_PREFIX}" ]; then
   echo -e "===\n=== Conda environment for build\n==="
   conda list