Remove @beta tag from apollo-boost install instruction
Remove @beta tag from apollo-boost install instruction

This keeps these docs consistent with the docs website, which might
help with people reading the docs on npmjs.
https://www.apollographql.com/docs/react/essentials/get-started.html#installation

apollostack/apollo-client,apollographql/apollo-client,apollostack/apollo-client,apollostack/apollo-client,apollographql/apollo-client