Remove deprecated style for diagrams

Author: jordanmccullough

_stylesheets/curriculum-beta.scss

@@ -75,11 +75,6 @@ html, body{
     margin: 0 auto;
   }
 
-  .diagram{
-    width: 60%;
-    /*margin: 0 auto;*/
-    text-align: center;
-  }
 
   .slide{
     min-height: 100%;