Remove collective API as alternative site

The alternative site "collective API" is broken.

README.md

@@ -46,8 +46,7 @@
     <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://www.public-apis.ml">Public APIs Site</a> •
-    <a href="https://apihouse.vercel.app">Apihouse</a> •
-    <a href="https://www.collective-api.ml">Collective APIs</a>
+    <a href="https://apihouse.vercel.app">Apihouse</a>
 </div>
 
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