MINOR: Update downloads.html (#441)

Fixes incorrect release year for 2.7.1 release.
diff --git a/downloads.html b/downloads.html
index 6cc07f9..78cf694 100644
--- a/downloads.html
+++ b/downloads.html
@@ -531,7 +531,7 @@
     <h3 class="download-version">2.7.1<a href="#2.7.1"><i class="fas fa-link " style="color:#053ce2"></i></a></h3>
     <ul>
         <li>
-            Released May 10, 2020
+            Released May 10, 2021
         </li>
         <li>
             <a href="https://archive.apache.org/dist/kafka/2.7.1/RELEASE_NOTES.html">Release Notes</a>