CI: replace obsolete set-output command

See: https://github.blog/changelog/2022-10-11-github-actions-\
     deprecating-save-state-and-set-output-commands/

Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>

Author: jiangxin

.github/workflows/git-pot.yml

@@ -43,9 +43,9 @@ jobs:
           ) &&
           if diff footprint.remote footprint.last
           then
-            echo ::set-output name=status::skip
+            echo "status=skip" >> $GITHUB_OUTPUT
           else
-            echo ::set-output name=status::no
+            echo "status=no" >> $GITHUB_OUTPUT
           fi
       - name: clone pot/${{ matrix.branch }} branch of current repository
         if: steps.skip-if-redundant.outputs.status != 'skip'