[ResponseOps][Docs]: Maintenance window GAing and category options removed

[nastasha-solomon]

Closes #2796 and #1885. Updates the maintenance windows docs as follows:

• Updates the page-level applies to tags to show that the feature is in tech preview for 9.0-91 and GA in 9.2 and Serverless.
• Removed the note at the top of the page that showed the feature was in tech preview.
• Adds a note that explains that category-specific maintenance window options are unavailable (removed) in 9.2 and Serverless. Also updated the first item in the note further down that explains how you can select only a single category when you turn on filters.
• Refreshes both images on the page since they show elements that are no longer available in 9.2 and Serverless (the tech preview label and the option to choose categories for the maintenance windows

Preview: https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2855/explore-analyze/alerts-cases/alerts/maintenance-windows

[github-actions]

🔍 Preview links for changed docs

• explore-analyze/alerts-cases/alerts/maintenance-windows.md

[js-jankisalvi]

Should we include the callout as shown below in explore-analyze/images/kibana-create-maintenance-window-filter.png screenshot?

[nastasha-solomon]

@js-jankisalvi I don't think we need to include the callout in the screenshot, mainly because doc'ing it won't add any extra value to the docs. That said, I do think this note would benefit from the detail about maintenance windows applying to all rule types in Serverless and 9.2+.

[theletterf]

Approved with a comment!

[js-jankisalvi]

Sorry my bad for not pointing out earlier, that removing category will cause MW to apply to all solutions, not all rule types.
nit: specified rule categories are removed and the maintenance window will be applied to all rules types. -> specified rule categories are removed and the maintenance window will be applied to rules in all solutions.

[nastasha-solomon]

Confirmed that tech preview label and category options are removed in the UI.