remove save-pr-number

.github/workflows/get-api-diff.yml

@@ -171,16 +171,3 @@ jobs:
         path: api-head.json
     - name: Kill Misskey Job
       run: screen -S misskey -X quit
-
-  save-pr-number:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo "$PR_NUMBER" > ./pr_number
-      - uses: actions/upload-artifact@v3
-        with:
-          name: api-artifact
-          path: pr_number