Update dependency fluentd to v1.19.3

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
fluentd	"= 1.14.6" → "= 1.19.3"

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: docker/estenrye/fluentd-cloudtrail/Gemfile.lock

Fetching gem metadata from https://rubygems.org/............
Resolving dependencies...

Bundler could not find compatible versions for gem "async-http":
  In snapshot (Gemfile.lock):
    async-http (= 0.59.2)

  In Gemfile:
    async-http (= 0.59.2)

    fluentd (= 1.19.3) was resolved to 1.19.3, which depends on
      async-http (~> 0.86)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.