Bump mongo from 2.18.2 to 2.19.3

Bumps [mongo](https://github.com/mongodb/mongo-ruby-driver) from 2.18.2 to 2.19.3.
- [Release notes](https://github.com/mongodb/mongo-ruby-driver/releases)
- [Changelog](https://github.com/mongodb/mongo-ruby-driver/blob/master/docs/release-notes.txt)
- [Commits](mongodb/mongo-ruby-driver@v2.18.2...v2.19.3)

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

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

Gemfile.lock

@@ -313,7 +313,7 @@ GEM
       ruby2_keywords (>= 0.0.5)
     momentjs-rails (2.29.4.1)
       railties (>= 3.1)
-    mongo (2.18.2)
+    mongo (2.19.3)
       bson (>= 4.14.1, < 5.0.0)
     mongoid (8.1.2)
       activemodel (>= 5.1, < 7.1, != 7.0.0)