[DOCS] Fixes command page titles

docs/reference/commands/certgen.asciidoc

@@ -1,9 +1,9 @@
 [role="xpack"]
 [testenv="gold+"]
 [[certgen]]
-== certgen
+== elasticsearch-certgen
 
-deprecated[6.1,Replaced by <<certutil,`certutil`>>.]
+deprecated[6.1,Replaced by <<certutil,`elasticsearch-certutil`>>.]
 
 The `elasticsearch-certgen` command simplifies the creation of certificate
 authorities (CA), certificate signing requests (CSR), and signed certificates

docs/reference/commands/saml-metadata.asciidoc

@@ -1,7 +1,7 @@
 [role="xpack"]
 [testenv="gold+"]
 [[saml-metadata]]
-== saml-metadata
+== elasticsearch-saml-metadata
 
 The `elasticsearch-saml-metadata` command can be used to generate a SAML 2.0 Service
 Provider Metadata file.

docs/reference/commands/users-command.asciidoc

@@ -1,10 +1,7 @@
 [role="xpack"]
 [testenv="gold+"]
 [[users-command]]
-== Users Command
-++++
-<titleabbrev>users</titleabbrev>
-++++
+== elasticsearch-users
 
 If you use file-based user authentication, the `elasticsearch-users` command
 enables you to add and remove users, assign user roles, and manage passwords.