Bump strong_migrations from 0.7.7 to 0.7.8 (#14412)

Bumps [strong_migrations](https://github.com/ankane/strong_migrations) from 0.7.7 to 0.7.8.
- [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/v0.7.7...v0.7.8)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -764,7 +764,7 @@ GEM
       dante (>= 0.2.0)
       multi_json (~> 1.0)
       stripe (> 5, < 6)
-    strong_migrations (0.7.7)
+    strong_migrations (0.7.8)
       activerecord (>= 5)
     test-prof (1.0.6)
     thor (1.1.0)