update what's new entry to 7.1

Author: eteq

index.html

@@ -110,7 +110,7 @@
     </section>
 
 <section class="whatsnew"><div id="prenew"></div>
-	What's new in <a href="https://docs.astropy.org/en/stable/whatsnew/7.0.html">Astropy 7.0</a>
+	What's new in <a href="https://docs.astropy.org/en/stable/whatsnew/7.1.html">Astropy 7.1</a>
 	<p class="version" id="core-package-version"></p>
 
 </section>