Update link this Public APIs Site

Ref: https://github.com/public-apis/public-apis/issues/1852#issuecomment-904676880

README.md

@@ -45,7 +45,7 @@
     <br />
     <a href="https://free-apis.github.io">Free APIs</a> •
     <a href="https://devresourc.es/tools-and-utilities/public-apis">Dev Resources</a> •
-    <a href="https://public-apis-site.vercel.app">Public APIs Site</a>
+    <a href="https://www.public-apis.ml">Public APIs Site</a>
 </div>
 
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