Bump strong_migrations from 0.4.1 to 0.4.2 (mastodon#12242)

Bumps [strong_migrations](https://github.com/ankane/strong_migrations) from 0.4.1 to 0.4.2.
- [Release notes](https://github.com/ankane/strong_migrations/releases)
- [Changelog](https://github.com/ankane/strong_migrations/blob/master/CHANGELOG.md)
- [Commits](ankane/strong_migrations@v0.4.1...v0.4.2)

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

Gemfile.lock

@@ -378,7 +378,7 @@ GEM
     mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.12.0)
+    minitest (5.12.2)
     msgpack (1.3.1)
     multi_json (1.13.1)
     multipart-post (2.1.1)
@@ -619,7 +619,7 @@ GEM
     stoplight (2.1.3)
     streamio-ffmpeg (3.0.2)
       multi_json (~> 1.8)
-    strong_migrations (0.4.1)
+    strong_migrations (0.4.2)
       activerecord (>= 5)
     temple (0.8.1)
     terminal-table (1.8.0)