chore(deps-dev): bump codecov in /fluent-plugin-kubernetes-sumologic

Bumps [codecov](https://github.com/codecov/codecov-ruby) from 0.2.12 to 0.6.0.
- [Release notes](https://github.com/codecov/codecov-ruby/releases)
- [Changelog](https://github.com/codecov/codecov-ruby/blob/master/CHANGELOG.md)
- [Commits](codecov/codecov-ruby@v0.2.12...v0.6.0)

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

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

fluent-plugin-kubernetes-sumologic/Gemfile.lock

@@ -10,9 +10,8 @@ GEM
   specs:
     addressable (2.8.0)
       public_suffix (>= 2.0.2, < 5.0)
-    codecov (0.2.12)
-      json
-      simplecov
+    codecov (0.6.0)
+      simplecov (>= 0.15, < 0.22)
     concurrent-ruby (1.1.10)
     cool.io (1.7.1)
     crack (0.4.5)
@@ -33,7 +32,6 @@ GEM
     hashdiff (1.0.1)
     http_parser.rb (0.8.0)
     httpclient (2.8.3)
-    json (2.6.3)
     msgpack (1.5.1)
     power_assert (2.0.3)
     public_suffix (2.0.5)
@@ -42,7 +40,7 @@ GEM
     serverengine (2.3.2)
       sigdump (~> 0.2.2)
     sigdump (0.2.5)
-    simplecov (0.22.0)
+    simplecov (0.21.2)
       docile (~> 1.1)
       simplecov-html (~> 0.11)
       simplecov_json_formatter (~> 0.1)