Clarify that custom finalizer names must be publicly qualified finalizer names

[ramalabeysekera]

Description

This PR updates the Finalizers concept documentation to clearly state that custom finalizer names must be fully qualified names.

While the Kubernetes API server enforces this validation at runtime, the current documentation does not explicitly mention the requirement, which can lead to confusion for users manually adding finalizers to objects.

This clarification helps users avoid validation errors when creating or updating resources with custom finalizers.

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• ✅ login: ramalabeysekera / name: Ramal Abeysekera (aaa4d95, 3bb1a9a, bbd9b90)

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[lmktfy]

Thanks. We don't normally use "fully qualified"; our jargon terms are public (known across multiple clusters) and private (eg for label keys).

Try this (also fixing style nits):

Suggested change

	{{<note>}}
	* Custom finalizer names must be fully qualified names, such as example.com/finalizer-name. Kubernetes enforces this format, and will reject resources that do not use qualified finalizer names.
	{{</note>}}
	{{< note >}}
	Custom finalizer names **must** be publicly qualified finalizer names, such as `example.com/finalizer-name`.
	Kubernetes enforces this format; the API server rejects writes to objects where the change does not use qualified finalizer names for any custom finalizer.
	{{< /note >}}

If you accept this change, please also update the commit message and PR title.

---

(nit)
This note is important, but it should appear later in the page. It is not so important that it should be part of the page overview.

[ramalabeysekera]

Thanks for reviewing this, I've made the requested changes just now