update expected output

test/expected_help.txt

@@ -673,6 +673,13 @@ COMMANDS
                     environment variables.  For example, log_procname in a
                     syslog message.
 
+  redirect-to <path>
+                    If a path is given, all output from commands, like
+                    ":echo" and when writing to stdout (e.g. :write-to -), will
+                    be sent to the given file.  If no path is specified, the
+                    current redirect will be cleared and output will be
+                    captured as it was before the redirect was done.
+
   session <cmd>     Add the given command to the session file
                     (~/.lnav/session).  Any commands listed in the session file
                     are executed on startup.  Only the highlight, word-wrap, and