nic: Update LTS docs

[sean-breen]

Proposed changes

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 Technical Writing Style Guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
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Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[AlexFenlon]

Few references to OSS to remove eg.

https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/tutorials/nginx-ingress-linkerd.md?plain=1#L9

https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/tutorials/nginx-ingress-osm.md?plain=1#L11

This says Plus only
https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/troubleshooting/troubleshoot-common.md?plain=1#L21

This entire page has a few things
https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/overview/nginx-plus.md?plain=1#L12

There are mentions of the stub status on this page in which we need to remove and only reference the NGINX Plus API
https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/overview/design.md?plain=1#L65

similar reasoning here.
https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/logging-and-monitoring/status-page.md?plain=1#L11

we can remove this note
https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/logging-and-monitoring/service-insight.md?plain=1#L9

reference to sticky sessions being in OSS

https://github.com/nginx/documentation/blob/chore/sb-lts-docs/content/nic/lts/install/migrate-ingress-nginx.md?plain=1#L425

[github-actions]

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