Update ToC display to use card instead of panel

assets/style/main.sass

@@ -181,11 +181,6 @@ h6, .content h6
   .reacts a.reaction
     display: inline-block
 
-.toc
-  @extend .panel
-  @extend .is-size-7
-  @extend .mt-4
-
   ul
     @extend .menu-list
 

layouts/partials/toc.html

@@ -1,7 +1,9 @@
 {{ if .Params.ShowTOC }}
-    <div class="toc">
-        <p class="panel-heading">Contents</p>
-        <div class="panel-block">
+    <div class="card mb-5">
+        <div class="card-header has-background-light">
+            <p class="card-header-title">Contents</p>
+        </div>
+        <div class="card-content content is-size-7">
             {{ .TableOfContents }}
         </div>
     </div>