include install action in cache key

Author: minrk

.github/actions/install-dependencies/action.yml

@@ -36,7 +36,7 @@ runs:
       with:
         path: ${{ env.CONDA }}/envs/mpi-tutorial
         key:
-          conda-env-${{ steps.get-date.outputs.today }}-${{ inputs.python-version }}-${{ hashFiles('environment.yml') }}
+          conda-env-${{ steps.get-date.outputs.today }}-${{ inputs.python-version }}-${{ hashFiles('environment.yml') }}-${{ hashFiles('.github/actions/install-dependencies/**') }}
 
     - name: Clear package cache
       # package cache seems to be stale