Update dawidd6/action-send-mail action to v4 (#9996)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/announce-lts-rc.yml

@@ -16,7 +16,7 @@ jobs:
           discourse-author-username: jenkins-release-bot
           discourse-category: 23
       - name: Post on mailing list
-        uses: dawidd6/action-send-mail@v3
+        uses: dawidd6/action-send-mail@v4
         with:
           server_address: smtp.gmail.com
           server_port: 465