doc: fix typographic error in process doc

An apostrophe was being used where a backtick was called for, resulting
in improper rendering.

PR-URL: https://github.com/nodejs/node/pull/7431
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Ingvar Stepanyan <me@rreverser.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/process.md

@@ -774,7 +774,7 @@ emitMyWarning();
 added: v0.7.7
 -->
 
-The `process.execArgv' property returns the set of Node.js-specific command-line
+The `process.execArgv` property returns the set of Node.js-specific command-line
 options passed when the Node.js process was launched. These options do not
 appear in the array returned by the [`process.argv`][] property, and do not
 include the Node.js executable, the name of the script, or any options following