docs(contributing): Fix README link to contributing docs (denoland#20526

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Fixing a broken link to the contributing docs

README.md

@@ -108,7 +108,7 @@ Deno.serve((_req) => new Response("Hello, World!"));
 We appreciate your help!
 
 To contribute, please read our
-[contributing instructions](https://deno.land/manual/contributing).
+[contributing instructions](https://deno.land/manual/references/contributing/).
 
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