man: fix typo in the alias symlink name

Symlink created by Alias will use the value as the file name.

(cherry picked from commit 3f0e7fd)
(cherry picked from commit a68188e)
(cherry picked from commit 4b8ce6a)
(cherry picked from commit e8566d7)
(cherry picked from commit 0179fb5)

Author: RadxaYuntian

man/systemd.unit.xml

@@ -165,13 +165,13 @@
     section. When the unit is enabled, symlinks will be created for those names, and removed when the unit is
     disabled. For example, <filename>reboot.target</filename> specifies
     <varname>Alias=ctrl-alt-del.target</varname>, so when enabled, the symlink
-    <filename>/etc/systemd/system/ctrl-alt-del.service</filename> pointing to the
+    <filename>/etc/systemd/system/ctrl-alt-del.target</filename> pointing to the
     <filename>reboot.target</filename> file will be created, and when
     <keycombo><keycap>Ctrl</keycap><keycap>Alt</keycap><keycap>Del</keycap></keycombo> is invoked,
-    <command>systemd</command> will look for the <filename>ctrl-alt-del.service</filename> and execute
-    <filename>reboot.service</filename>. <command>systemd</command> does not look at the [Install] section at
-    all during normal operation, so any directives in that section only have an effect through the symlinks
-    created during enablement.</para>
+    <command>systemd</command> will look for <filename>ctrl-alt-del.target</filename>, follow the symlink to
+    <filename>reboot.target</filename>, and execute <filename>reboot.service</filename> as part of that target.
+    <command>systemd</command> does not look at the [Install] section at all during normal operation, so any
+    directives in that section only have an effect through the symlinks created during enablement.</para>
 
     <para>Along with a unit file <filename>foo.service</filename>, the directory
     <filename>foo.service.wants/</filename> may exist. All unit files symlinked from such a directory are