Update dawidd6/action-send-mail action to v7

Author: renovate[bot]

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

@@ -17,7 +17,7 @@ jobs:
           discourse-author-username: jenkins-release-bot
           discourse-category: 23
       - name: Post on mailing list
-        uses: dawidd6/action-send-mail@6d98ae34d733f9a723a9e04e94f2f24ba05e1402 # v6
+        uses: dawidd6/action-send-mail@6e71c855c9a091d80a519621b9fd3e8d252ca40c # v7
         with:
           server_address: smtp.gmail.com
           server_port: 465