ci: Get api.json from Misskeyでupload-artifact@v4で同名artifactでエラーになるのを修正 (#12770)

* ci: upload-artifact@v4で同名artifactでエラーになるのを修正

Co-authored-by: おさむのひと <46447427+samunohito@users.noreply.github.com>

* report-api-diff.ymlの最中にエラーが発生したときに分かりづらいので、PRにコメントを残すようにする

* 古いget-api-diffを使ってるactionとの互換性をもたせる

---------

Co-authored-by: おさむのひと <46447427+samunohito@users.noreply.github.com>

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

@@ -56,7 +56,7 @@ jobs:
     - name: Upload Artifact
       uses: actions/upload-artifact@v4
       with:
-        name: api-artifact
+        name: api-artifact-${{ matrix.api-json-name }}
         path: ${{ matrix.api-json-name }}
 
   save-pr-number:
@@ -69,5 +69,5 @@ jobs:
           echo "$PR_NUMBER" > ./pr_number
       - uses: actions/upload-artifact@v4
         with:
-          name: api-artifact
+          name: api-artifact-pr-number
           path: pr_number