nixos/manual: add dummy ids to silence warnings

nixos/doc/manual/administration/running.xml

@@ -4,7 +4,7 @@
       version="5.0"
       xml:id="ch-running">
  <title>Administration</title>
- <partintro>
+ <partintro xml:id="ch-running-intro">
   <para>
    This chapter describes various aspects of managing a running NixOS system,
    such as how to use the <command>systemd</command> service manager.

nixos/doc/manual/configuration/configuration.xml

@@ -4,7 +4,7 @@
       version="5.0"
       xml:id="ch-configuration">
  <title>Configuration</title>
- <partintro>
+ <partintro xml:id="ch-configuration-intro">
   <para>
    This chapter describes how to configure various aspects of a NixOS machine
    through the configuration file

nixos/doc/manual/development/development.xml

@@ -4,7 +4,7 @@
         version="5.0"
         xml:id="ch-development">
  <title>Development</title>
- <partintro>
+ <partintro xml:id="ch-development-intro">
   <para>
    This chapter describes how you can modify and extend NixOS.
   </para>

nixos/doc/manual/installation/installation.xml

@@ -4,7 +4,7 @@
       version="5.0"
       xml:id="ch-installation">
  <title>Installation</title>
- <partintro>
+ <partintro xml:id="ch-installation-intro">
   <para>
    This section describes how to obtain, install, and configure NixOS for
    first-time use.