Remove broken frozen API link from index-basics.md

[Copilot]

The frozen index API was removed in Elasticsearch, causing the documentation link to return 404.

Changes

• Removed broken operation-indices-unfreeze API link from badge filter descriptions (2 occurrences)
• Updated text from "follower index, rollup index, or frozen" to "follower index or rollup index"
• Applied consistently across both serverless and stack documentation tabs

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Update broken API link on Index basics page</issue_title>
<issue_description>On the Index basics page, the frozen link to the API docs results in a 404. </issue_description>

<agent_instructions>Remove the link that 404's and update the text in that sentence accordingly</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@lcawl FYI That API was removed in https://github.com/elastic/elasticsearch/pull/119227 and there's rationale for the removal in https://www.elastic.co/guide/en/elasticsearch/reference/8.19/unfreeze-index-api.html @bmorelli25 sorry this is easy

• Fixes Update broken API link on Index basics page #3354

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[github-actions]

🔍 Preview links for changed docs

• manage-data/data-store/index-basics.md

[kilfoyle]

LGTM! 🌵
Well done, Copilot!