Bump strong_migrations from 0.3.0 to 0.3.1 (#9015)

Bumps [strong_migrations](https://github.com/ankane/strong_migrations) from 0.3.0 to 0.3.1.
- [Release notes](https://github.com/ankane/strong_migrations/releases)
- [Changelog](https://github.com/ankane/strong_migrations/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ankane/strong_migrations/compare/v0.3.0...v0.3.1)

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

Gemfile.lock

@@ -585,7 +585,7 @@ GEM
     stoplight (2.1.3)
     streamio-ffmpeg (3.0.2)
       multi_json (~> 1.8)
-    strong_migrations (0.3.0)
+    strong_migrations (0.3.1)
       activerecord (>= 3.2.0)
     temple (0.8.0)
     terminal-table (1.8.0)