Move option brackets outside of <varname> per APSG

https://help.apple.com/applestyleguide/#/apsg1fde7568

> Use … regular text for the brackets that enclose something that’s optional

Signed-off-by: Roger Sheen <roger@infotexture.net>

resources/conref-task.dita

@@ -91,7 +91,7 @@
                   on each transformation.</note>
               </p>
             </li>
-            <li id="options"><varname>[options]</varname> include the following optional build parameters:
+            <li id="options">[<varname>options</varname>] include the following optional build parameters:
               <parml conref="../parameters/dita-command-arguments.dita#dita-command-properties/dita_build_options">
                 <plentry>
                   <pt/>

topics/using-dita-command.dita

@@ -22,7 +22,7 @@
       </step>
       <step>
         <cmd>At the command-line prompt, enter the following command:</cmd>
-        <info><codeblock><filepath conref="../resources/conref-task.dita#ID/dita-cmd"/> <parmname>--input</parmname>=<varname>input-file</varname> <parmname>--format</parmname>=<varname>format</varname> <varname audience="expert">[options]</varname></codeblock>
+        <info><codeblock><filepath conref="../resources/conref-task.dita#ID/dita-cmd"/> <parmname>--input</parmname>=<varname>input-file</varname> <parmname>--format</parmname>=<varname>format</varname> <ph audience="expert">[<varname>options</varname>]</ph></codeblock>
           <p>where:</p>
           <ul>
             <li conref="../resources/conref-task.dita#ID/novice-variables-1"