Bump mini_racer from 0.6.3 to 0.12.0

Bumps [mini_racer](https://github.com/discourse/mini_racer) from 0.6.3 to 0.12.0.
- [Changelog](https://github.com/rubyjs/mini_racer/blob/main/CHANGELOG)
- [Commits](rubyjs/mini_racer@v0.6.3...v0.12.0)

---
updated-dependencies:
- dependency-name: mini_racer
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -251,7 +251,7 @@ GEM
     librato-metrics (2.1.2)
       aggregate (~> 0.2.2)
       faraday
-    libv8-node (16.10.0.0)
+    libv8-node (21.7.2.0)
     listen (3.8.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
@@ -276,8 +276,8 @@ GEM
     mime-types-data (3.2022.0105)
     mini_mime (1.1.2)
     mini_portile2 (2.8.4)
-    mini_racer (0.6.3)
-      libv8-node (~> 16.10.0.0)
+    mini_racer (0.12.0)
+      libv8-node (~> 21.7.2.0)
     minitest (5.19.0)
     mock_redis (0.36.0)
       ruby2_keywords