Docs: Explain closing the high level client

It looks like we weren't clear on when and why you should close the high
level client and folks were closing it after every request which is not
efficient. This explains why you should close the client and when so
this shouldn't be as common.

Closes #32001

Author: nik9000

docs/java-rest/high-level/getting-started.asciidoc

@@ -127,12 +127,11 @@ include-tagged::{doc-tests}/MainDocumentationIT.java[rest-high-level-client-init
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 The high-level client will internally create the low-level client used to
-perform requests based on the provided builder, and manage its lifecycle.
-
-The high-level client instance needs to be closed when no longer needed so that
-all the resources used by it get properly released, as well as the underlying
-http client instance and its threads. This can be done through the `close`
-method, which will close the internal `RestClient` instance.
+perform requests based on the provided builder. That low-level client
+maintains a pool of connections and starts some threads so you should
+close the high-level client when you are well and truly done with
+it and it will in turn close the internal low-level client to free those
+resources. This can be done through the `close`:
 
 ["source","java",subs="attributes,callouts,macros"]
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