Teach the miri cronjobs to speak politely

.github/workflows/ci.yml

@@ -130,5 +130,5 @@ jobs:
           ZULIP_API_TOKEN: ${{ secrets.ZULIP_API_TOKEN }}
         run: |
           ~/.local/bin/zulip-send --stream miri --subject "Cron Job Failure" \
-            --message '@**RalfJ** @**oli** the Miri cron job build failed. Please investigate!' \
+            --message 'Dear @**RalfJ** and @**oli**\n\nIt would appear that the Miri cron job build failed. Would you mind investigating this issue?\n\nThanks in advance!\nSincerely,\nThe Miri Cronjobs Bot' \
             --user $ZULIP_BOT_EMAIL --api-key $ZULIP_API_TOKEN --site https://rust-lang.zulipchat.com