fix font style source code filename

Author: Lachlan Campbell

docs/typography/font-style/index.html

@@ -105,7 +105,7 @@ <h1 class="f4 ttu tracked fw6">Reference</h1>
       </div>
       <section class="bg-near-white black-70 pt4 pb5">
         <header class="ph3 ph5-ns pt4">
-          <kbd class="yellow">src/_font-weights.css</kbd>
+          <kbd class="yellow">src/_font-style.css</kbd>
         </header>
 <pre class="ph3 ph5-ns">
 <code class="code" style="font-size: .75rem;">

src/templates/docs/font-style/index.html

@@ -72,7 +72,7 @@ <h1 class="f4 ttu tracked fw6">Reference</h1>
       </div>
       <section class="bg-near-white black-70 pt4 pb5">
         <header class="ph3 ph5-ns pt4">
-          <kbd class="yellow">src/_font-weights.css</kbd>
+          <kbd class="yellow">src/_font-style.css</kbd>
         </header>
 <pre class="ph3 ph5-ns">
 <code class="code" style="font-size: .75rem;">