fix what gets commited to automated grants

Author: honzajavorek

.github/workflows/generate_grants.yml

@@ -20,6 +20,7 @@ jobs:
       uses: peter-evans/create-pull-request@v7
       with:
         token: ${{ secrets.GITHUB_TOKEN }}
+        add-paths: ./operations/grants.rst
         commit-message: "update the list of grants (generated)"
         branch: automation/grants
         title: "Automated update of the list of grants"