Fix broken Slack digest for new comments (#9455)

* Correctly compare GitHub username to lead label
* Parenthesize generator expression
* Set `next` default to empty string
* Actually paranthesize generator expression

---------

Co-authored-by: jchamp <jchamp@archive.org>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Mek <michael.karpeles@gmail.com>
Co-authored-by: Scott Barnes <scottreidbarnes@gmail.com>

scripts/gh_scripts/issue_comment_bot.py

@@ -217,7 +217,12 @@ def comment_on_thread(message: str):
             if lead['leadLabel'] == i['lead_label']
         )
         slack_id = next(
-            lead['slackId'] for lead in leads if lead['leadLabel'] == username
+            (
+                lead['slackId']  # type: ignore[syntax]
+                for lead in leads
+                if lead['leadLabel'] == f'Lead: @{username}'
+            ),
+            '',
         )
         if slack_id:
             message += f'Lead: {slack_id}\n'