github action: fix minor issue

Author: wkliao

.github/workflows/pnetcdf_c_master.yml

@@ -83,7 +83,7 @@ jobs:
         pip install numpy cython cftime pytest twine wheel check-manifest
         export MPICC=$MPICH_DIR/bin/mpicc
         pip install mpi4py
-        pip install torch, torchvision
+        pip install torch torchvision
 
     - name: Install PnetCDF-Python
       run: |

.github/workflows/pnetcdf_c_official.yml

@@ -81,7 +81,7 @@ jobs:
         pip install numpy cython cftime pytest twine wheel check-manifest
         export MPICC=$MPICH_DIR/bin/mpicc
         pip install mpi4py
-        pip install torch, torchvision
+        pip install torch torchvision
 
     - name: Install PnetCDF-Python
       run: |