doc: edit module introduction

The module introduction includes some uninformative text and some
repetitive text. Edit for clarity and brevity.

PR-URL: #17463
Reviewed-By: Gireesh Punathil <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Daniel Bevenius <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Jon Moss <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: Trott

doc/api/modules.md

@@ -6,10 +6,8 @@
 
 <!--name=module-->
 
-Node.js has a simple module loading system.  In Node.js, files and modules
-are in one-to-one correspondence (each file is treated as a separate module).
-
-As an example, consider a file named `foo.js`:
+In the Node.js module system, each file is treated as a separate module. For
+example, consider a file named `foo.js`:
 
 ```js
 const circle = require('./circle.js');