Replace deprecated set-output with GITHUB_OUTPUT

Replace the deprecated `::set-output` workflow command with appending output
key-value pairs to $GITHUB_OUTPUT.

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

.github/workflows/update.yml

@@ -38,7 +38,7 @@ jobs:
         run: |
           git add -- cedict_1_0_ts_utf-8_mdbg.txt
           git diff --cached --stat
-          echo "::set-output name=changed::$(git diff --cached --quiet; echo $?)"
+          echo "changed=$(git diff --cached --quiet; echo $?)" >> "$GITHUB_OUTPUT"
       - name: "Update metadata"
         if: "fromJSON(steps.diff.outputs.changed)"
         run: |