PBCKP-782 doc added note in Remote Mode section

Author: oleg gurev

doc/Readme.md

@@ -3,3 +3,6 @@
 xmllint --noout --valid probackup.xml
 xsltproc stylesheet.xsl probackup.xml >pg-probackup.html
 ```
+> [!NOTE]
+>Install ```docbook-xsl``` if you got
+>``` "xsl:import : unable to load http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"``` 

doc/pgprobackup.xml

@@ -1970,6 +1970,14 @@ pg_probackup restore -B <replaceable>backup_dir</replaceable> --instance <replac
       for communication between the hosts.
      </para>
     </note>
+    <note>
+      <para>
+       In addition to SSH connection, <application>pg_probackup</application> uses
+       a regular connection to the database to manage the remote operation.
+       See <xref linkend="pbk-configuring-the-database-cluster"/> for details of how to set up
+       a database connection.
+      </para>
+     </note>
     <para>
       The typical workflow is as follows:
     </para>