Fix program listing and detail page styling

lms/templates/learner_dashboard/certificate_status.underscore

@@ -7,6 +7,6 @@
     <a href="<%- certificate_url %>" class="btn-brand cta-secondary">
         <% // safe-lint: disable=underscore-not-escaped %>
         <span class="certificate-icon blue-certificate-icon" aria-hidden="true"><%= certificateSvg %></span>
-        <%- gettext('View/Share Certificate') %>
+        <%- gettext('View Certificate') %>
     </a>
 </div>

lms/templates/learner_dashboard/course_enroll.underscore

@@ -1,7 +1,7 @@
 <% if (is_enrolled) { %>
     <div class="enrollment-info"><%- gettext('enrolled') %></div>
     <% if (is_enrollment_open || is_course_ended) { %>
-        <a href="<%- course_url %>" class="btn-neutral btn view-course-link">
+        <a href="<%- course_url %>" class="btn view-course-link">
             <% if (is_enrollment_open) { %>
                 <%- gettext('View Course') %>
             <% } else if (is_course_ended) { %>

lms/templates/learner_dashboard/empty_programs_list.underscore

@@ -1,6 +1,6 @@
 <section class="empty-programs-message">
     <h2 class="hd-3"><%- gettext('You are not enrolled in any programs yet.') %></h2>
-    <a class="btn-neutral" href="<%- marketingUrl %>">
+    <a class="btn-brand" href="<%- marketingUrl %>">
         <span class="icon fa fa-search" aria-hidden="true"></span>
         <span><%- gettext('Explore Programs') %></span>
     </a>

lms/templates/learner_dashboard/explore_new_programs.underscore

@@ -2,7 +2,7 @@
     <%- gettext('Browse recently launched courses and see what\'s new in your favorite subjects') %>
 </div>
 <div class="ad-link">
-    <a href="<%- marketingUrl %>" class="btn-neutral">
+    <a href="<%- marketingUrl %>" class="btn new-programs-btn">
         <span class="icon fa fa-search" aria-hidden="true"></span>
         <span><%- gettext('Explore New Programs') %></span>
     </a>