doc: require() tries first core not native modules

Change a single word in documentation with a more precise one.

Native is a module compiled in machine "native" code.
A module normally written in a compiled language, not in JavaScript.

Core modules form Node's built-in "core" functionalities.
You don't need to install them. They are included in every Node installation
and documented in https://nodejs.org/api/ .

PR-URL: https://github.com/nodejs/node/pull/10324
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Italo A. Casas <me@italoacasas.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/modules.md

@@ -368,11 +368,11 @@ example, then `require('./some-library')` would attempt to load:
 
 <!--type=misc-->
 
-If the module identifier passed to `require()` is not a native module,
+If the module identifier passed to `require()` is not a
-and does not begin with `'/'`, `'../'`, or `'./'`, then Node.js starts at the
+[core](#modules_core_modules) module, and does not begin with `'/'`, `'../'`, or
-parent directory of the current module, and adds `/node_modules`, and
+`'./'`, then Node.js starts at the parent directory of the current module, and
-attempts to load the module from that location. Node will not append
+adds `/node_modules`, and attempts to load the module from that location. Node
-`node_modules` to a path already ending in `node_modules`.
+will not append `node_modules` to a path already ending in `node_modules`.
 
 If it is not found there, then it moves to the parent directory, and so
 on, until the root of the file system is reached.