update h2 style

src/client/styles/scss/_wiki.scss

@@ -44,7 +44,7 @@ div.body {
     border-bottom: solid 1px transparent;
   }
   h2 {
-    padding-bottom: 0.5em;
+    padding-bottom: 0.3em;
     font-size: 1.6em;
     font-weight: bold;
     line-height: 1.225;