Bump strong_migrations from 1.8.0 to 2.1.0

Bumps [strong_migrations](https://github.com/ankane/strong_migrations) from 1.8.0 to 2.1.0.
- [Changelog](https://github.com/ankane/strong_migrations/blob/master/CHANGELOG.md)
- [Commits](ankane/strong_migrations@v1.8.0...v2.1.0)

---
updated-dependencies:
- dependency-name: strong_migrations
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Gemfile.lock

@@ -488,16 +488,16 @@ GEM
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
     stringio (3.1.1)
-    strong_migrations (1.8.0)
-      activerecord (>= 5.2)
+    strong_migrations (2.1.0)
+      activerecord (>= 6.1)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
     terser (1.2.4)
       execjs (>= 0.3.0, < 3)
     thor (1.3.2)
     thread_safe (0.3.6)
     tilt (2.1.0)
-    timeout (0.4.1)
+    timeout (0.4.2)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
     unicode-display_width (2.6.0)