improve(css): make governance subtitle match home page style

Author: chriskrycho

templates/governance/index.hbs

@@ -3,7 +3,7 @@
 <header class="mt3 mt2-ns mb4 mb5-ns tc tl-ns">
   <div class="w-100 mw-none ph3 mw8-m mw9-l center f3">
     <h1>Governance</h1>
-    <h2 class="subtitle">How Rust is built by its community</h2>
+    <h2 class="f2 f1-ns mt0">How Rust is built by its community</h2>
   </div>
 </header>