Build(deps): Bump logster from 2.7.1 to 2.8.0 (#9310)

This includes Font Awesome upgrade to version 5.

Bumps [logster](https://github.com/discourse/logster) from 2.7.1 to 2.8.0.
- [Release notes](https://github.com/discourse/logster/releases)
- [Changelog](https://github.com/discourse/logster/blob/master/CHANGELOG.md)
- [Commits](https://github.com/discourse/logster/compare/v2.7.1...v2.8.0)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Gemfile.lock

@@ -172,7 +172,7 @@ GEM
     logstash-event (1.2.02)
     logstash-logger (0.26.1)
       logstash-event (~> 1.2)
-    logster (2.7.1)
+    logster (2.8.0)
     loofah (2.4.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)