Bump stringio from 3.0.7 to 3.0.8

Bumps [stringio](https://github.com/ruby/stringio) from 3.0.7 to 3.0.8.
- [Release notes](https://github.com/ruby/stringio/releases)
- [Changelog](https://github.com/ruby/stringio/blob/master/NEWS.md)
- [Commits](ruby/stringio@v3.0.7...v3.0.8)

---
updated-dependencies:
- dependency-name: stringio
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

Gemfile.lock

@@ -231,7 +231,7 @@ GEM
       sprockets (>= 3.0.0)
     sql_queries_count (0.0.1)
       rails (> 3.0.0)
-    stringio (3.0.7)
+    stringio (3.0.8)
     thor (1.2.2)
     tilt (2.2.0)
     time (0.2.2)