doc: ensure consistent grammar in node.1 file

PR-URL: https://github.com/nodejs/node/pull/6426
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

doc/node.1

@@ -59,7 +59,7 @@ Syntax check the script without executing.
 
 .TP
 .BR \-i ", " \-\-interactive
-Opens the REPL even if stdin does not appear to be a terminal.
+Open the REPL even if stdin does not appear to be a terminal.
 
 .TP
 .BR \-r ", " \-\-require " " \fImodule\fR
@@ -88,7 +88,7 @@ Print stack traces for process warnings (including deprecations).
 
 .TP
 .BR \-\-trace\-sync\-io
-Prints a stack trace whenever synchronous I/O is detected after the first turn
+Print a stack trace whenever synchronous I/O is detected after the first turn
 of the event loop.
 
 .TP