fix CodeMirror height

Author: phtournier

source/_static/css/codemirror.css

@@ -3,7 +3,6 @@
 .CodeMirror {
   /* Set height, width, borders, and global font properties here */
   font-family: monospace;
-  height: 300px;
   color: black;
   direction: ltr;
   flex: 1;