man: drop some left-over mentions of StandardOutput=syslog

We dropped them from the StandardOuput= documentation long ago, but
elswhere some references where lurking.

man/sd-daemon.xml

@@ -70,10 +70,9 @@
 
     <para>These prefixes are intended to be used in conjunction with stderr-based logging (or stdout-based
     logging) as implemented by systemd. If a systemd service definition file is configured with
-    <varname>StandardError=journal</varname>, <varname>StandardError=syslog</varname> or
-    <varname>StandardError=kmsg</varname> (and similar with <varname>StandardOutput=</varname>), these
-    prefixes can be used to encode a log level in lines printed. This is similar to the kernel
-    <function>printk()</function>-style logging. See
+    <varname>StandardError=journal</varname> or <varname>StandardError=kmsg</varname> (and similar with
+    <varname>StandardOutput=</varname>), these prefixes can be used to encode a log level in lines
+    printed. This is similar to the kernel <function>printk()</function>-style logging. See
     <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> for more
     information.</para>
 

man/systemd.exec.xml

@@ -66,9 +66,9 @@
       will also gain an automatic <varname>After=</varname> dependency on
       <citerefentry><refentrytitle>systemd-tmpfiles-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para></listitem>
 
-      <listitem><para>Units whose standard output or error output is connected to <option>journal</option>,
-      <option>syslog</option> or <option>kmsg</option> (or their combinations with console output, see below)
-      automatically acquire dependencies of type <varname>After=</varname> on
+      <listitem><para>Units whose standard output or error output is connected to <option>journal</option> or
+      <option>kmsg</option> (or their combinations with console output, see below) automatically acquire
+      dependencies of type <varname>After=</varname> on
       <filename>systemd-journald.socket</filename>.</para></listitem>
 
       <listitem><para>Units using <varname>LogNamespace=</varname> will automatically gain ordering and