chore(deps): bump net-http-persistent in /fluent-plugin-events

Bumps [net-http-persistent](https://github.com/drbrain/net-http-persistent) from 4.0.2 to 4.0.4.
- [Release notes](https://github.com/drbrain/net-http-persistent/releases)
- [Changelog](https://github.com/drbrain/net-http-persistent/blob/master/History.txt)
- [Commits](drbrain/net-http-persistent@v4.0.2...v4.0.4)

---
updated-dependencies:
- dependency-name: net-http-persistent
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

fluent-plugin-events/Gemfile.lock

@@ -23,7 +23,7 @@ GEM
       public_suffix (>= 2.0.2, < 6.0)
     bigdecimal (3.1.8)
     concurrent-ruby (1.1.10)
-    connection_pool (2.4.0)
+    connection_pool (2.4.1)
     cool.io (1.7.1)
     crack (1.0.0)
       bigdecimal
@@ -86,7 +86,7 @@ GEM
       ruby2_keywords (>= 0.0.5)
     msgpack (1.5.1)
     multipart-post (2.4.1)
-    net-http-persistent (4.0.2)
+    net-http-persistent (4.0.4)
       connection_pool (~> 2.2)
     power_assert (2.0.3)
     public_suffix (5.0.5)