Update `api-routes-graphql` README Link (#15350)

examples/api-routes-graphql/README.md

 # API routes with GraphQL server
 
-Next.js ships with [API routes](https://github.com/vercel/next.js#api-routes), which provide an easy solution to build your own `API`. This example shows their usage alongside [apollo-server-micro](https://github.com/apollographql/apollo-server/tree/master/packages/apollo-server-micro) to provide simple GraphQL server consumed by Next.js app.
+Next.js ships with [API routes](https://github.com/vercel/next.js#api-routes), which provide an easy solution to build your own `API`. This example shows their usage alongside [apollo-server-micro](https://github.com/apollographql/apollo-server/tree/main/packages/apollo-server-micro) to provide simple GraphQL server consumed by Next.js app.
 
 ## Deploy your own