Docs: Update Vue School BTS 21 banner (#1139)

Author: nicodevs

docs/.vitepress/components/BannerTop.vue

@@ -11,10 +11,7 @@
         <img src="/images/vueschool/vs-backpack.png" alt="Backpack">
       </div>
       <div class="vs-slogan">
-        3-months Vue School for only $49 <span style="text-decoration: line-through">$75</span>!
-        <span class="vs-slogan-light">
-          Limited Time Offer
-        </span>
+        Less than <span class="vs-slogan-light">48 hours</span> left for the Vue School offer
       </div>
       <div class="vs-button">
         GET ACCESS