Adjust default link header value in netlify plugin readme (#3723)

packages/gatsby-plugin-netlify/README.md

@@ -39,7 +39,7 @@ plugins: [
       headers: {}, // option to add more headers. `Link` headers are transformed by the below criteria
       allPageHeaders: [], // option to add headers for all pages. `Link` headers are transformed by the below criteria
       mergeSecurityHeaders: true, // boolean to turn off the default security headers
-      mergeLinkHeaders: false, // boolean to turn off the default gatsby js headers (disabled by default, until gzip is fixed for server push)
+      mergeLinkHeaders: true, // boolean to turn off the default gatsby js headers
       mergeCachingHeaders: true, // boolean to turn off the default caching headers
       transformHeaders: (headers, path) => headers, // optional transform for manipulating headers under each path (e.g.sorting), etc.
     },