[8.15] Update the Uptime deprecation and removal details (#192707) (#…

…192822)

# Backport

This will backport the following commits from `main` to `8.15`:
- [Update the Uptime deprecation and removal details
(#192707)](#192707)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

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the Uptime deprecation and removal details (#192707)\n\n##
Summary\r\n\r\nThere has been an updated decision not to remove the
Uptime app from\r\n9.0.0, but will be done in a future version, in early
2026.\r\n\r\nThe wording of the deprecation/removal notice in the 8.15.0
release note\r\nhas been updated to reflect this.\r\n\r\n###
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Summary\r\n\r\nThere has been an updated decision not to remove the
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2026.\r\n\r\nThe wording of the deprecation/removal notice in the 8.15.0
release note\r\nhas been updated to reflect this.\r\n\r\n###
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Summary\r\n\r\nThere has been an updated decision not to remove the
Uptime app from\r\n9.0.0, but will be done in a future version, in early
2026.\r\n\r\nThe wording of the deprecation/removal notice in the 8.15.0
release note\r\nhas been updated to reflect this.\r\n\r\n###
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Co-authored-by: Paul Bianciardi <[email protected]>

docs/CHANGELOG.asciidoc

@@ -179,11 +179,11 @@ you make the necessary updates after you upgrade to 8.15.0.
 
 [discrete]
 [[deprecation-uptime]]
-.Uptime is deprecated in 8.15.0 and will be removed in 9.0.0.
+.Uptime is deprecated in 8.15.0 and will be removed in a future version.
 [%collapsible]
 ====
 *Details* +
-The Uptime app is already hidden from Kibana when there is no recent Heartbeat data, but will be completely removed in 9.0.0. You should migrate to Synthetics as an alternative. For more details, refer to the {observability-guide}/uptime-intro.html[Uptime documentation].
+The Uptime app is already hidden from Kibana when there is no recent Heartbeat data, and will be completely removed in early 2026. You should migrate to Synthetics as an alternative. For more details, refer to the {observability-guide}/uptime-intro.html[Uptime documentation].
 ====
 
 [float]