[7.17] docs: remove xpack.apm.searchAggregatedTransactions (#149896) (#149902)

# Backport

This will backport the following commits from `main` to `7.17`:
- [docs: remove `xpack.apm.searchAggregatedTransactions`
(#149896)](#149896)

<!--- Backport version: 8.9.7 -->

### Questions ?
Please refer to the [Backport tool
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remove `xpack.apm.searchAggregatedTransactions` (#149896)\n\n###
Summary\r\n\r\nThis PR reverts
#82379 and
removes\r\n`xpack.apm.searchAggregatedTransactions` from the
documentation. This is\r\nfor
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remove `xpack.apm.searchAggregatedTransactions` (#149896)\n\n###
Summary\r\n\r\nThis PR reverts
#82379 and
removes\r\n`xpack.apm.searchAggregatedTransactions` from the
documentation. This is\r\nfor
https://github.com/elastic/apm-server/pull/10140:\r\n\r\n> Removing
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remove `xpack.apm.searchAggregatedTransactions` (#149896)\n\n###
Summary\r\n\r\nThis PR reverts
#82379 and
removes\r\n`xpack.apm.searchAggregatedTransactions` from the
documentation. This is\r\nfor
https://github.com/elastic/apm-server/pull/10140:\r\n\r\n> Removing
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BACKPORT-->

Author: bmorelli25

docs/settings/apm-settings.asciidoc

@@ -80,11 +80,6 @@ Maximum number of child items displayed when viewing trace details. Defaults to
 `xpack.observability.annotations.index` {ess-icon}::
 Index name where Observability annotations are stored. Defaults to `observability-annotations`.
 
-`xpack.apm.searchAggregatedTransactions` {ess-icon}::
-Enables Transaction histogram metrics. Defaults to `auto` so the UI will use metric indices over transaction indices for transactions if aggregated transactions are found. When set to `always`, additional configuration in APM Server is required. When set to `never` and aggregated transactions are not used. 
-+
-See {apm-guide-ref}/transaction-metrics.html[Configure transaction metrics] for more information.
-
 `xpack.apm.metricsInterval` {ess-icon}::
 Sets a `fixed_interval` for date histograms in metrics aggregations. Defaults to `30`.