DOC-2898: Documentation enhancements: for https://www.tiny.cloud/docs/tinymce/latest/custom-toggle-toolbar-button/

[jeslynbo]

Ticket: DOC-2898

Site: Staging branch

Changes:

• Simplified onSetup event handling and teardown logic
• Replacing plain inline code with a cross-referenced API link
• Edited comments for onSetup demo
• Ensure {product name} is being used correctly

Pre-checks:

• Branch prefixed with feature/<version>/, hotfix/<version>/, staging/<version>/, or release/<version>/.
• modules/ROOT/nav.adoc has been updated (if applicable).
• Included a release note entry for any New product features.
• If this is a minor release, updated productminorversion in antora.yml and added new supported versions entry in modules/ROOT/partials/misc/supported-versions.adoc.

Review:

• Documentation Team Lead has reviewed

[kemister85]

Good improvements overall — the restructured explanation, clearer option/API descriptions, and the formatChanged documentation with unbind() are all valuable. A few issues to fix before merge (suggestions provided inline so you can commit them directly).

[kemister85]

Duplicated paragraph — remove the first occurrence.

Suggested change

	The `+formatChanged+` method accepts the following parameters:
	The `+vars+` argument controls which variables are used to match the content when determining whether to run the callback. This argument is only used when `+similar+` is `+false+`.
	The `+formatChanged+` method accepts the following parameters:
	The `+formatChanged+` method accepts the following parameters: