Content headings shouldn't use MP

Author: ArtOfCode-

_assets/css/headers.scss

@@ -1,7 +1,11 @@
-h1, h2, h3, h4, h5, h6 {
+h1 {
   font-family: 'Maven Pro', serif;
 }
 
+h2, h3, h4, h5, h6 {
+  font-family: 'Fira Sans', sans-serif;
+}
+
 h1 {
   font-size: 3em;
   font-variant: small-caps;