Update release-1.15 to Hugo version 0.57.2

[zacharysarah]

This PR reintroduces #16094, which replicates #16104 and #16151 for release-1.15.

Fixes #16066

Context

#16066 exhibits behavior characteristic of gohugoio/hugo#5615. To resolve the issue, we need to upgrade Hugo to a version that includes the solution.

Because #16094 got lost in the release timing shuffle, this PR didn't make it into release-1.15 before 1.16 was released. This PR also needs to be introduced into master in a separate PR.

/sig docs
/priority important-soon

/assign @aimeeu

[aimeeu]

End user acceptance testing https://deploy-preview-16813--k8s-v1-15.netlify.com/

• "latest version" link in deprecation warning on k8s.io points to https://kubernetes.io/docs/home/ (from issue 16606)
• "latest version" link in deprecation warning on k8s.io/docs/home points to https://kubernetes.io/docs/home/ (from issue 16606)
• links on Home page point to 1.15 version
• reference API docs 1.15 version and buttons work
• eyeball links on various pages to make sure they all point to 1.15

Locally:

1. Fetch the PR
2. run from <website_dir>: $ make check-hugo-versions

• output states the Hugo versions match between Makefile and netlify.toml

3. Install Hugo version specified and compile site using hugo server
   • One compile warning:

   Building sites … WARN 2019/10/11 10:59:15 Content directory "/home/aimee/Dev/git/github.com/aimeeu/k8s/sigdocs/website/content/en/docs/reference/kubernetes-api" have both index.* and _index.* files, pick one.
   

• Docs smoke test page renders correctly

4. Build the Docker container

• make docker-image builds a Docker image with the Hugo version specified in the makefile
• make docker-serve executes without error

---

Based on my random testing, I'd say this is good to push once the makefile has been updated.

[aimeeu]

@zacharysarah - @kbhawkey pointed out in PR #16814 that the Makefile needs to be updated. Should be do that here as well to keep the Hugo version in sync between the Makefile and netlify.toml?

[zacharysarah]

@aimeeu

@kbhawkey pointed out in PR #16814 that the Makefile needs to be updated. Should be do that here as well to keep the Hugo version in sync between the Makefile and netlify.toml?

Done!

[zacharysarah]

@zparnold Please wrangle when ready. 🤠

[zacharysarah]

/assign @bradtopol

[jimangel]

/lgtm
/approve

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