doc: fix spurious whitespace

doc/functions/appimagetools.xml

@@ -52,7 +52,7 @@ spot sensor temperature 0.000000, unit celsius, color scheme 0, calibration: off
 
 <prompt>$ </prompt>file -k type2.AppImage
 type2.AppImage: ELF 64-bit LSB executable, x86-64, version 1 (SYSV) (Lepton 3.x), scale 232-60668, spot sensor temperature -4.187500, color scheme 15, show scale bar, calibration: offset -0.000000, slope 0.000000 (Lepton 2.x), scale 4111-45000, spot sensor temperature 412442.250000, color scheme 3, minimum point enabled, calibration: offset -75402534979642766821519867692934234112.000000, slope 5815371847733706829839455140374904832.000000, dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.18, BuildID[sha1]=79dcc4e55a61c293c5e19edbd8d65b202842579f, stripped\012- data
-  </screen>
+</screen>
 
   <para>
    Note how the type 1 AppImage is described as an <literal>ISO 9660 CD-ROM

doc/functions/dockertools.xml

@@ -537,7 +537,7 @@ exportImage {
 
   name = someLayeredImage.name;
 }
-  </programlisting>
+</programlisting>
   </example>
 
   <para>

doc/functions/prefer-remote-fetch.xml

@@ -10,16 +10,16 @@
   upload while the builder can fetch faster directly from the source. To use
   it, put the following snippet as a new overlay:
 <programlisting>
-    self: super:
-      (super.prefer-remote-fetch self super)
-  </programlisting>
+self: super:
+  (super.prefer-remote-fetch self super)
+</programlisting>
   A full configuration example for that sets the overlay up for your own
   account, could look like this
-<programlisting>
-    $ mkdir ~/.config/nixpkgs/overlays/
-    $ cat &gt; ~/.config/nixpkgs/overlays/prefer-remote-fetch.nix &lt;&lt;EOF
-      self: super: super.prefer-remote-fetch self super
-    EOF
-  </programlisting>
+<screen>
+<prompt>$ </prompt>mkdir ~/.config/nixpkgs/overlays/
+<prompt>$ </prompt>cat &gt; ~/.config/nixpkgs/overlays/prefer-remote-fetch.nix &lt;&lt;EOF
+  self: super: super.prefer-remote-fetch self super
+EOF
+</screen>
  </para>
 </section>

doc/functions/trivial-builders.xml

@@ -35,25 +35,25 @@
      An example of using <literal>runCommand</literal> is provided below.
     </para>
 <programlisting>
-       (import &lt;nixpkgs&gt; {}).runCommand "my-example" {} ''
-         echo My example command is running
+(import &lt;nixpkgs&gt; {}).runCommand "my-example" {} ''
+  echo My example command is running
 
-         mkdir $out
+  mkdir $out
 
-         echo I can write data to the Nix store > $out/message
+  echo I can write data to the Nix store > $out/message
 
-         echo I can also run basic commands like:
+  echo I can also run basic commands like:
 
-         echo ls
-         ls
+  echo ls
+  ls
 
-         echo whoami
-         whoami
+  echo whoami
+  whoami
 
-         echo date
-         date
-       ''
-     </programlisting>
+  echo date
+  date
+''
+</programlisting>
    </listitem>
   </varlistentry>
   <varlistentry>