tree-wide: drop quotes from around [section]

For users, the square brackets already serve as markup and clearly delineate
the section name from surrounding text. Putting additional markup around that
only adds clutter. Also, we were very inconsistent in using the quotes. Let's
just drop them altogether.

man/daemon.xml

@@ -357,7 +357,7 @@
       special target unit <filename>sockets.target</filename>. It is
       recommended to place a
       <varname>WantedBy=sockets.target</varname> directive in the
-      <literal>[Install]</literal> section to automatically add such a
+      [Install] section to automatically add such a
       dependency on installation of a socket unit. Unless
       <varname>DefaultDependencies=no</varname> is set, the necessary
       ordering dependencies are implicitly created for all socket
@@ -520,7 +520,7 @@
         operating system-independent.</para></listitem>
 
         <listitem><para>Make sure to include an
-        <literal>[Install]</literal> section including installation
+        [Install] section including installation
         information for the unit file. See
         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
         for details. To activate your service on boot, make sure to