fix jumping in Chrome iOS.

Not sure if I should put this back if/when Chome iOS fixes this

https://bugs.chromium.org/p/chromium/issues/detail?id=720048

threejs/lessons/resources/lesson.css

@@ -372,12 +372,6 @@ pre.prettyprint, code.prettyprint {
     }
 }
 
-@media (max-height: 700px) {
-    .threejs_example {
-        height: 400px;
-    }
-}
-
 @media (max-width: 720px) {
     body {
         font-size: 16px;
@@ -385,6 +379,9 @@ pre.prettyprint, code.prettyprint {
     h1 {
         font-size: 24px;
     }
+    .threejs_example {
+        max-height: 400px;
+    }
     iframe {
         max-width: 95%;
     }