style: adjust newsletter component style

pages/index.js

@@ -92,13 +92,8 @@ export default function Home({ posts }) {
         </div>
       )}
       {siteMetadata.newsletter.provider !== '' && (
-        <div className="flex flex-col md:flex-row justify-between items-center">
-          <h1 className="text-3xl font-extrabold tracking-tight text-gray-900 dark:text-gray-100 sm:text-4xl md:text-6xl ">
-            Newsletter
-          </h1>
-          <div className="p-5">
-            <FormSubscribe />
-          </div>
+        <div className="flex items-center justify-center pt-4">
+          <FormSubscribe />
         </div>
       )}
     </>