fix wording and css of Bug Modal

client/less/main.less

@@ -1156,7 +1156,6 @@ and (max-width : 400px)  {
   .modal-header .close {
     font-size: 30px;
     padding-left: 10px;
-    margin-top: 22px;
   }
 
   .modal-header {

common/app/routes/challenges/components/Bug-Modal.jsx

@@ -39,7 +39,7 @@ export class BugModal extends PureComponent {
         <Modal.Body className='text-center'>
           <h3>
             Before you submit a new issue,
-            read "Help I've Found a Bug" and
+            read "How to Report a Bug" and
             browse other issues with this challenge.
           </h3>
           <Button
@@ -49,7 +49,7 @@ export class BugModal extends PureComponent {
             href={ bugLink }
             target='_blank'
             >
-            Read "Help I've Found a Bug"
+            Read "How to Report a Bug"
           </Button>
           <Button
             block={ true }