some rendering and syntax errors on k8s logstash pages

[shainaraskas]

Summary

• fixes [Website]: --- (Document Separator) is missing in the example configuration file (YAML). #5952
• fixes [Website]: The indication for 2 and 3 is missing in the setting example. #5951

advanced-configuration-logstash.md

• Fixed typo: "To do, this" → "To do this"
• Added missing --- YAML document separator between the Secret and Logstash resources

logstash-plugins.md

• Fixed broken link for logstash-filter-ruby (added missing URL)
• Fixed {version} → {{version.stack}} and added subs=true to the code fence
• Fixed missing closing " on last_metadata_path value
• Fixed missing closing " on temporary_directory value
• Changed code block language from shell to yaml
• Changed bare callout markers (<2>, <3>) to // <2>, // <3> for valid syntax inside code blocks

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes to find additional syntax errors
• No

[github-actions]

🔍 Preview links for changed docs

• deploy-manage/deploy/cloud-on-k8s/advanced-configuration-logstash.md
• deploy-manage/deploy/cloud-on-k8s/logstash-plugins.md

[github-actions]

Vale Linting Results

Summary: 1 warning found

⚠️ Warnings (1)

File	Line	Rule	Message
deploy-manage/deploy/cloud-on-k8s/logstash-plugins.md	95	Elastic.Articles	Use 'an SQL' instead of 'a SQL'. The article depends on pronunciation, not spelling.

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