Build(deps): Bump rails_failover from 0.7.3 to 0.8.1 (#15962)

Bumps [rails_failover](https://github.com/discourse/rails_failover) from 0.7.3 to 0.8.1.
- [Release notes](https://github.com/discourse/rails_failover/releases)
- [Changelog](https://github.com/discourse/rails_failover/blob/main/CHANGELOG.md)
- [Commits](https://github.com/discourse/rails_failover/compare/v0.7.3...v0.8.1)

---
updated-dependencies:
- dependency-name: rails_failover
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

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

Gemfile.lock

@@ -327,10 +327,10 @@ GEM
       nokogiri (>= 1.6)
     rails-html-sanitizer (1.4.2)
       loofah (~> 2.3)
-    rails_failover (0.7.3)
-      activerecord (~> 6.0)
+    rails_failover (0.8.1)
+      activerecord (> 6.0, < 7.1)
       concurrent-ruby
-      railties (~> 6.0)
+      railties (> 6.0, < 7.1)
     rails_multisite (4.0.0)
       activerecord (> 5.0, < 7)
       railties (> 5.0, < 7)