Fix broken API anchor links

[kingdonb]

These were obscured in the pre-release checks because some structural changes to the API docs hadn't been merged yet.

We can merge these changes straight away, or wait a few minutes and I'll have more corrections based on the reporting output. I think that most (>50%) of the errors I'm seeing are actually properly redirected, so it's taking a bit of effort to see whether each bad link on the report is a bogon or a valid issue to follow up. Should be over in a few minutes though.

[kingdonb]

The remaining "bad links" in the report are now corralled to two types: 1. the calendar link on the main page which has for some reason ZgotmplZ in it, (I think we made up some fields and the template errors out) and 2. blog links which refer to the old singular API style, that is properly redirected but not canonicalized. (and 3. this one: fluxcd/image-automation-controller#578)

Since I think we should update the link checker to follow redirects and not report them as errors, I'm going to leave those un-canonicalized for now, they don't hurt anything. (Here are the examples I'm talking about)

<style type="text/css"></style>

link_source	bad_link
https://fluxcd.io/blog/2021/09/september-2021-update/	https://fluxcd.io/flux/components/notification/provider/#writing-a-provider-spec
https://fluxcd.io/blog/2021/11/december-update/	https://fluxcd.io/flux/components/notification/provider/#slack
https://fluxcd.io/blog/2022/01/january-update/	https://fluxcd.io/flux/components/kustomize/kustomization/#hashicorp-vault
https://fluxcd.io/blog/2022/03/february-update/	https://fluxcd.io/flux/components/notification/provider/#grafana
https://fluxcd.io/blog/2022/03/february-update/	https://fluxcd.io/flux/components/notification/alert/#example
https://fluxcd.io/blog/2022/03/february-update/	https://fluxcd.io/flux/components/kustomize/kustomization/#post-build-variable-substitution
https://fluxcd.io/blog/2022/04/march-update/	https://fluxcd.io/flux/components/kustomize/kustomization/#azure-key-vault-secret-entry
https://fluxcd.io/blog/2022/07/june-2022-update/	https://fluxcd.io/flux/components/notification/provider/#setting-up-the-github-dispatch-provider
https://fluxcd.io/blog/2022/08/manage-kyverno-policies-as-ocirepositories/	https://fluxcd.io/flux/components/kustomize/kustomization/#patches
https://fluxcd.io/blog/2022/08/manage-kyverno-policies-as-ocirepositories/	https://fluxcd.io/flux/components/kustomize/kustomization/#dependencies

If you follow these links in a browser or with redirects following enabled, then you can see they all work. I'll update the link checker to not flag them as errors anymore, before we merge it in #1630.

[stefanprodan]

LGTM

Thanks @kingdonb 🏅