Replace large Linux sample with rbtree.c

public/index.html

@@ -37,9 +37,9 @@
     <section id="samples">
       <p class="samples-label">Try a sample:</p>
       <div class="samples-grid">
-        <button class="sample-btn" data-url="https://github.com/torvalds/linux/blob/master/kernel/sched/fair.c">
+        <button class="sample-btn" data-url="https://github.com/torvalds/linux/blob/master/lib/rbtree.c">
           <span class="sample-lang">C</span>
-          <span class="sample-name">Linux Kernel — sched/fair.c</span>
+          <span class="sample-name">Linux Kernel — rbtree.c</span>
         </button>
         <button class="sample-btn" data-url="https://github.com/redis/redis/blob/unstable/src/t_zset.c">
           <span class="sample-lang">C</span>