Educator 1560 - Clean up labelling in the Discussion Add Post form

common/static/common/templates/discussion/thread-type.underscore

 <div class="post-field">
-    <label class="field-label">
+<fieldset>
+    <legend class="field-label">
         <span class="field-label-text">
             <% // Translators: This is the label for a control to select a forum post type %>
             <%- gettext("Post type") %>
         </span>
+    </legend>
     <div class="field-help" id="field_help_post_type">
         <%- gettext("Questions raise issues that need answers. Discussions share ideas and start conversations. (Required)") %>
     </div>
     <div class="field-label">
-            <fieldset class="field-input">
-                <legend class="sr"><%- gettext("Post type") %></legend>
         <label for="<%= form_id %>-post-type-question" class="post-type-label">
             <input aria-describedby="field_help_post_type" type="radio" name="<%= form_id %>-post-type" class="field-input input-radio" id="<%= form_id %>-post-type-question" value="question">
             <span class="field-input-label">
@@ -26,7 +26,5 @@
                 <%- gettext("Discussion") %>
             </span>
         </label>
-            </fieldset>
     </div>
-    </label>
-</div>
+</fieldset>

common/static/common/templates/discussion/topic.underscore

-<label class="field-label">
-    <span class="field-label-text">
+<div class="field-label">
+    <label for="topic" class="field-label-text">
         <%- gettext("Topic area") %>
-    </span>
+    </label>
     <div class="field-help" id="field_help_topic_area">
         <%- gettext("Add your post to a relevant topic to help others find it. (Required)") %>
     </div>
-    <div class="field-input">
-        <select class="post-topic field-input" aria-describedby="field_help_topic_area wrapper-visibility-message" required>
+</div>
+<div class="field-input">
+    <select id="topic" class="post-topic field-input" aria-describedby="field_help_topic_area wrapper-visibility-message" required>
         <%= edx.HtmlUtils.ensureHtml(topics_html) %>
     </select>
-    </div>
-</label>
+</div>

lms/static/sass/discussion/views/_create-edit-post.scss

@@ -47,7 +47,6 @@
       }
 
       .field-label-text {
-        margin: $baseline 0 0 0;
         display: block;
       }
 
@@ -67,7 +66,7 @@
       line-height: 1.5;
 
       &#field_help_post_type {
-        @include margin($baseline / 2, 0, $baseline * 0.75, 0);
+        @include margin($baseline / 4, 0, $baseline * 0.75, 0);
       }
 
       &#new-post-editor-description {