Bump chartkick from 5.1.2 to 5.1.3

Bumps [chartkick](https://github.com/ankane/chartkick) from 5.1.2 to 5.1.3.
- [Changelog](https://github.com/ankane/chartkick/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ankane/chartkick/compare/v5.1.2...v5.1.3)

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

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

Gemfile.lock

@@ -102,7 +102,7 @@ GEM
       msgpack (~> 1.2)
     builder (3.3.0)
     byebug (11.1.3)
-    chartkick (5.1.2)
+    chartkick (5.1.3)
     coderay (1.1.3)
     concurrent-ruby (1.3.5)
     connection_pool (2.5.0)