fixed jump to top bug on edit form cancel button click

lms/static/coffee/src/discussion/views/discussion_thread_view.coffee

@@ -170,6 +170,7 @@ if Backbone?
       @renderSubView(@showView)
 
     cancelEdit: (event) =>
+      event.preventDefault()
       @createShowView()
       @renderShowView()
 

lms/static/sass/_discussion.scss

@@ -272,10 +272,14 @@ body.discussion {
 
   .edit-post-form {
     width: 100%;
-    margin-bottom: 20px;
+    margin-bottom: 40px;
     @include clearfix;
     @include box-sizing(border-box);
 
+    h1 {
+      font-size: 20px;
+    }
+
     .form-row {
       margin-top: 20px;
     }