Remove check for fs.realpath.native support, since it's everywhere (#887)

Author: RyanZim

lib/fs/index.js

@@ -61,6 +61,7 @@ Object.keys(fs).forEach(key => {
 api.forEach(method => {
   exports[method] = u(fs[method])
 })
+exports.realpath.native = u(fs.realpath.native)
 
 // We differ from mz/fs in that we still ship the old, broken, fs.exists()
 // since we are a drop-in replacement for the native module
@@ -123,8 +124,3 @@ if (typeof fs.writev === 'function') {
     })
   }
 }
-
-// fs.realpath.native only available in Node v9.2+
-if (typeof fs.realpath.native === 'function') {
-  exports.realpath.native = u(fs.realpath.native)
-}