[DOCS] Update install instructions for Debian/Ubuntu (elastic#84645)

The use of `apt-key` is deprecated and will no longer be available after
Debian 11 and Ubuntu 22.04. This updates the installation instructions
for Debian-based distributions.

Closes elastic#84644

docs/reference/setup/install/deb.asciidoc

@@ -22,7 +22,7 @@ include::key.asciidoc[]
 
 [source,sh]
 -------------------------
-wget -qO - https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add -
+wget -qO - https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo gpg --dearmor -o /usr/share/keyrings/elasticsearch-keyring.gpg
 -------------------------
 
 [[deb-repo]]
@@ -49,7 +49,7 @@ ifeval::["{release-state}"=="released"]
 
 ["source","sh",subs="attributes,callouts"]
 --------------------------------------------------
-echo "deb https://artifacts.elastic.co/packages/{major-version}/apt stable main" | sudo tee /etc/apt/sources.list.d/elastic-{major-version}.list
+echo "deb [signed-by=/usr/share/keyrings/elasticsearch-keyring.gpg] https://artifacts.elastic.co/packages/{major-version}/apt stable main" | sudo tee /etc/apt/sources.list.d/elastic-{major-version}.list
 --------------------------------------------------
 
 endif::[]
@@ -58,7 +58,7 @@ ifeval::["{release-state}"=="prerelease"]
 
 ["source","sh",subs="attributes,callouts"]
 --------------------------------------------------
-echo "deb https://artifacts.elastic.co/packages/{major-version}-prerelease/apt stable main" | sudo tee /etc/apt/sources.list.d/elastic-{major-version}.list
+echo "deb [signed-by=/usr/share/keyrings/elasticsearch-keyring.gpg] https://artifacts.elastic.co/packages/{major-version}-prerelease/apt stable main" | sudo tee /etc/apt/sources.list.d/elastic-{major-version}.list
 --------------------------------------------------
 
 endif::[]