Polish SHA comparison in reference doc (#46432)

* Polish SHA comparison in reference doc

* Update targz.asciidoc

docs/setup/install/targz.asciidoc

@@ -32,13 +32,13 @@ The Linux archive for Kibana v{version} can be downloaded and installed as follo
 
 ["source","sh",subs="attributes"]
 --------------------------------------------
-wget https://artifacts.elastic.co/downloads/kibana/kibana-{version}-linux-x86_64.tar.gz
-shasum -a 512 kibana-{version}-linux-x86_64.tar.gz <1>
+curl -O https://artifacts.elastic.co/downloads/kibana/kibana-{version}-linux-x86_64.tar.gz
+curl https://artifacts.elastic.co/downloads/kibana/kibana-{version}-linux-x86_64.tar.gz.sha512 | shasum -a 512 -c - <1>
 tar -xzf kibana-{version}-linux-x86_64.tar.gz
 cd kibana-{version}-linux-x86_64/ <2>
 --------------------------------------------
-<1> Compare the SHA produced by `shasum` with the
-    https://artifacts.elastic.co/downloads/kibana/kibana-{version}-linux-x86_64.tar.gz.sha512[published SHA].
+<1> Compares the SHA of the downloaded `.tar.gz` archive and the published checksum, which should output
+    `kibana-{version}-linux-x86_64.tar.gz: OK`.
 <2> This directory is known as `$KIBANA_HOME`.
 
 endif::[]
@@ -60,12 +60,12 @@ The Darwin archive for Kibana v{version} can be downloaded and installed as foll
 ["source","sh",subs="attributes"]
 --------------------------------------------
 curl -O https://artifacts.elastic.co/downloads/kibana/kibana-{version}-darwin-x86_64.tar.gz
-shasum -a 512 kibana-{version}-darwin-x86_64.tar.gz <1>
+curl https://artifacts.elastic.co/downloads/kibana/kibana-{version}-darwin-x86_64.tar.gz.sha512 | shasum -a 512 -c - <1>
 tar -xzf kibana-{version}-darwin-x86_64.tar.gz
 cd kibana-{version}-darwin-x86_64/ <2>
 --------------------------------------------
-<1> Compare the SHA produced by `shasum` with the
-    https://artifacts.elastic.co/downloads/kibana/kibana-{version}-darwin-x86_64.tar.gz.sha512[published SHA].
+<1> Compares the SHA of the downloaded `.tar.gz` archive and the published checksum, which should output
+    `kibana-{version}-darwin-x86_64.tar.gz: OK`.
 <2> This directory is known as `$KIBANA_HOME`.
 
 Alternatively, you can download the following package, which contains only