Bump slack-notifier from 2.3.2 to 2.4.0

Bumps [slack-notifier](https://github.com/stevenosloan/slack-notifier) from 2.3.2 to 2.4.0.
- [Release notes](https://github.com/stevenosloan/slack-notifier/releases)
- [Changelog](https://github.com/slack-notifier/slack-notifier/blob/main/changelog.md)
- [Commits](slack-notifier/slack-notifier@2.3.2...2.4.0)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -1626,7 +1626,7 @@ GEM
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    slack-notifier (2.3.2)
+    slack-notifier (2.4.0)
     sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)