Update about-release-schedule.hbs (#3479)

Fix the image dimensions to be what we end up with instead of the original ones.

Author: XhmikosR

layouts/about-release-schedule.hbs

@@ -14,7 +14,7 @@
         {{{ contents }}}
 
         <p>
-          <img src="https://raw.githubusercontent.com/nodejs/Release/master/schedule.svg?sanitize=true" alt="{{ title }}" width="960" height="500">
+          <img src="https://raw.githubusercontent.com/nodejs/Release/master/schedule.svg?sanitize=true" alt="{{ title }}" width="760" height="396">
         </p>
 
         {{{ release-schedule }}}