Bump mysql2 from 0.5.3 to 0.5.4

Bumps [mysql2](https://github.com/brianmario/mysql2) from 0.5.3 to 0.5.4.
- [Release notes](https://github.com/brianmario/mysql2/releases)
- [Commits](https://github.com/brianmario/mysql2/compare/0.5.3...0.5.4)

---
updated-dependencies:
- dependency-name: mysql2
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Gemfile.lock

@@ -170,7 +170,7 @@ GEM
     minitest (5.15.0)
     minitest-stub-const (0.6)
     mocha (1.14.0)
-    mysql2 (0.5.3)
+    mysql2 (0.5.4)
     nio4r (2.5.8)
     nokogiri (1.13.6)
       mini_portile2 (~> 2.8.0)
@@ -349,7 +349,7 @@ DEPENDENCIES
   listen
   minitest-stub-const
   mocha
-  mysql2 (~> 0.5.3)
+  mysql2 (~> 0.5.4)
   pg (~> 1.3.5)
   puma (~> 5.6)
   rack-mini-profiler