Build(deps): Bump logster from 2.6.3 to 2.7.0 (#9050)

This includes a new feature that allows you to control the length of log messages via `Logster.config.maximum_message_length`. More details at: https://github.com/discourse/logster/commit/e5c4fc0b6ee6fe662094a6d8dc7281c7bcd343c3

Bumps [logster](https://github.com/discourse/logster) from 2.6.3 to 2.7.0.
- [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/v2.6.3...v2.7.0)

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

Gemfile.lock

@@ -171,7 +171,7 @@ GEM
     logstash-event (1.2.02)
     logstash-logger (0.26.1)
       logstash-event (~> 1.2)
-    logster (2.6.3)
+    logster (2.7.0)
     loofah (2.4.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)