[DOCS] Add missing index to test setup

#19884 fixed the aliases, but didn't add `index2` to the test setup which causes the
alias command to fail

docs/reference/indices/aliases.asciidoc

@@ -22,7 +22,7 @@ POST /_aliases
 }
 --------------------------------------------------
 // CONSOLE
-// TEST[s/^/PUT test1\n/]
+// TEST[s/^/PUT test1\nPUT test2\n/]
 
 An alias can also be removed, for example: