adjust codemirror window on raw HTML editor

common/lib/xmodule/xmodule/css/html/edit.scss

-// HTML component editor: 
+// HTML component editor:
 .html-editor {
   @include clearfix();
 
   .CodeMirror {
     @include box-sizing(border-box);
-    position: absolute;
-    top: 46px;
-    width: 100%;
-    height: 379px;
-    border: 1px solid #3c3c3c;
-    border-top: 1px solid #8891a1;
-    background: #fff;
-    color: #3c3c3c;
-  }
-
-  .CodeMirror-scroll {
-    height: 100%;
-  }
-
-  .editor-tabs {
-    top: 0 !important;
-    right: 10px;
-    z-index: 99;
+    height: 435px;
   }
 
   .is-inactive {
     display: none;
   }
-}
\ No newline at end of file
+}