Bump scout_apm from 2.6.7 to 2.6.8

Bumps [scout_apm](https://github.com/scoutapp/scout_apm_ruby) from 2.6.7 to 2.6.8.
- [Release notes](https://github.com/scoutapp/scout_apm_ruby/releases)
- [Changelog](https://github.com/scoutapp/scout_apm_ruby/blob/master/CHANGELOG.markdown)
- [Commits](scoutapp/scout_apm_ruby@v2.6.7...v2.6.8)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

Gemfile.lock

@@ -324,7 +324,7 @@ GEM
       sprockets (> 3.0)
       sprockets-rails
       tilt
-    scout_apm (2.6.7)
+    scout_apm (2.6.8)
       parser
     sentry-raven (3.0.0)
       faraday (>= 1.0)